Installing an intake manifold is very simple as far as the level of complication involved in general mechanics. However there are some "Do's and Don'ts" that every professional auto tech follows, mostly because they have had to redo a job in the past, maybe several of them.
Here's some tips;
First off DON'T use silicone RTV around the intake port seals. If you want a demonstration of why, squeeze out a blob on something and let it cure for a couple of days and then drop it into a cup of gasoline. After a little while is will swell up and eventually dissolve away to nothing. That's not to mention that it will squeeze out into the intake ports and create a "blockage ring" that will severely compromise flow. THEN it will dissolve as the gas/air mix washes over it when the engine is running, and this stuff all goes right on through the engine. You can use the silicone ring gaskets because the ring is back away from the edge of the port and the gasket itself is what comes in contact with the fuel mix. The ring is a second line of defense and these gaskets work very well. The ONLY sealer product that will not dissolve in gasoline is Permatex Aircraft grade sealer and that is what almost all professionals use.
CLEAN the head surfaces, the end seal surfaces, and the sealing surfaces of the manifold with some type of solvent that dries completely. I use alcohol or brake cleaner. The main point is that there is no oil left on the surfaces - sealer wont seal to oil.
So, with a standard intake gasket wipe silicone on around the water ports on the end of each head SPARINGLY with your finger, and drag a little line out to the end seal area. Then squeeze a large line of silicone (at least a 1/4") across each end seal boss on the block. Don't bother even pulling the cork or rubber end seals out of the package. Those are a throwback to the days before good quality automotive silicone and won't do you a lick of good today.
USE guide studs in the 4 corner bolts - one on the end of each head. You can make these easily by buying long bolts and cutting off the heads and grinding these off smooth and rounded. Screw them in finger tight.
Lay the intake gaskets on the gasket card with the "This side up" down. Brush a fairly healthy layer of Permatex Aircraft sealer around each intake port ring. Then set each seal down over the guide studs on the heads ("This side up" up) and seat the lower corners down even into the silicone on the end seals.
Brush another fairly healthy coat of Permatex Aircraft sealer around the ports on the intake manifold, and then LIGHTLY spread silicone around the water passages on each end of both sides and do a small wipe over to the end seal corners, (Remember to do the front and back on both sides - even though there is no passages on the rear, it still needs to be sealed).
Then just set the manifold down over the guide studs. On many engines the intake bolts need to be sealed, if only so oil won't climb the bolts and leak out under the bolt heads. I use the Pematex as it gives a good torque value and does not harden so you can retorque later without a problem. Use a very small dab on the threads, it doesn't take much.
Drop all the bolts into the unused holes and starting in 2 opposing holes (one on each side) of the middle holes - tighten these center bolts "2 finger tight". (That means holding the ratchet close to the head between your thumb and first finger). Then progressively do the rest like that. Now remove the guide studs and do those four. Now do all the bolts "2 finger tight " again, they will all be loose again at this point.
Almost done. Now torque the intake using the factory pattern and spec, and then do it again and again until no bolts pull up when you draw the torque. Let it sit for about 1 hour and do it again one more time.
OK, now walk away until tomorrow and torque it again. You're done. I've been using this procedure for many years and never have a leak, or sealing problem on the ports. I hope this helps save you a lot of hassles.