This is not a simple job to do, but it can be done with the proper tools and about a day's worth of work. I did mine about 2 weeks ago and it took a full day. Tear down took me about 1.5 hours. This included cleaning and careful removal of components due to the leak and accumulation of crap around the intake manifold/ head mating area.
Both of my gaskets were bad and provided a slow leak when the engine was cold and never leaked when it was up to full operation temperature. Cleaning takes several hours to do as it is not an easy task to keep contaminants and dirt from falling into the valley between the heads. I used a vacuum and a scraper at the same time to evacuate all the debris from the mating areas and the clogged water ports.
Here are the steps broken down if I remember correctly.
Raise vehicle high enough and drain coolant from entire system. Make sure you don't raise it too high that you cannot access the engine bay, but high enough for you to get under and access the large A/C and power steering bracket. Remove all cooling hoses attached to manifold. No need to remove water pump or EGR valve.
Remove all upper intake related parts, hoses, egr bypass tube, and related electrical connections (even the ones that go to the alternator, A/C compressor, ignition modules, and distributor) attached to intake manifold. If you have a bungee cord handy, wrap it around the main wire loom that crosses over the intake manifold and hook it to the holes/cutouts under the hood's internal bracing. Doing this with the loom simplifies removal and reinstalling manifold if you're doing this by yourself without a helper holding up the crossover wire loom. Then remove the ignition coil/module assembly.
Remove the distributor. Take off the distributor cap. Turn the engine over until the distributor is pointing at something easy to remember. I usually get the little arrow pointing at the passenger side headlight. It would be wise to line up the harmonic balancer line with the mark on the timing cover before the distributor is removed. Once this is done I remove the distributor
NOTE: Don't turn the engine after the distributor is removed.
Remove the hard fuel lines (relieve the fuel pressure first) attached to fuel distribution block. You should remove the two rear fittings as well that run down to the incoming and return lines.
Remove Air conditioning compressor without detaching lines and swing over to side while providing support underneath the compressor.
After this remove the two long bolts and nut that hold the aluminum A/C bracket to the block.
Now go under the vehicle and remove the 3 nuts that hold the power steering pump and bracket to the block. No need to detach the pump from the large aluminum bracket. Then go back up to the top and swing the bracket out of the way in a forward direction. No need to remove, just move it far forward enough to expose the bolt that holds the intake manifold down on the left front corner (driver's side). At this point you should have what appears to be a basic engine with a modern ABS intake plenum sitting on top. No need to remove the upper plenum. I did remove the MAP sensor as it sits a little high. This was done so that I don't break it while flipping the manifold assembly afterwords for cleaning.
Remove the intake manifold. Use a criss cross pattern to remove the manifold from the block. Start from the outer bolts, then work your way towards the center. On mine, all the bolts were actually loose and some were even finger tight.
There will be some coolant remaining if you didn't drain the radiator completely. Before you take the manifold off, do a thorough cleaning of the area around the intake manifold mating areas next to the heads and block. This ensures you don't have any surprise debris falling into the engine. The manifold will be stuck on due to the RTV that holds the ends down. Carefully pry off and wiggle it loose. At this point you can lift up and remove it. Remember the bungee recommendation? This is where you will appreciate the wire loom not hanging up on the manifold while removing on you own.
Clean up all mating surfaces with a gasket scraper. Make sure RTV is removed from all gasket surfaces. Clean out all coolant passages.
On mine the coolant passages looked like clogged arteries ( passenger rearmost cooling port). Luckily it was just the block off at the intake manifold. I guess the leak with small amounts air introduced into the cooling system caused a catalytic reaction and formed hard deposits and buildup at the point of infiltration in the gasket. The driver's side rearmost coolant port even appeared to have coolant mixing with water as there was a small muddy/milky mess. Luckily, there was no oil in the cooling system though.
After cleaning up all mating surfaces on the intake manifold, heads, and block, apply RTV to the front and rear surfaces of the block. Make sure you have enough to compress when the intake manifold is placed on top to form a good seal. I added about 3/16" tall and wide bead. Apply RTV to the topside and bottom-side of the new intake gaskets around the coolant passages. Do this sparingly as it does not need much. Just extra insurance incase it reoccurs in the future if the plastic gaskets fail again. Make sure you do not disturb the RTV and carefully place the intake manifold assembly straight down without twisting or rotating it. If you do happen to do this you can ruin the RTV seal and must reapply the RTV again.
Once the manifold is situated, torque the eight bolts in the correct sequence, 5-6-2-4-3-1-7-8 three separate times. The first time torque each to 89 inch lbs. The second time torque each to 106 inch lbs. The third time torque each to 132 inch lbs.
The rest of reassembly is reverse of removal for the external, and electrical components.
EDIT: Make sure you get the distributor back in the way it came out. You will need to make sure that it seats fully.
You will want to flush out the cooling system thoroughly and refill with the proper coolant along with distilled water and make sure you bleed the system properly to avoid getting trapped air in cooling system.
Test drive vehicle and make sure you have no leaks and performance is ok.