Parts and Tools
Since in the process of replacing the intake manifold gasket you will expose other hard-to-get-to parts, I decided to also replace some of these parts, such as the distributor gear, cap and rotor. The distributor cap and rotor cost about $30 at the local store. I purchased the distributor gear from the local Chevy dealer for $48.
As soon as I had all parts and gaskets that I needed for this repair, I also started gathering some important tools: torque wrench (the one with the 'click') is an absolute MUST, I bought an additional tube of 'Permatex sensor-safe Ultra Copper High Temp RTV Silicone Gasket Maker' from AutoZone and a 'Permatex Medium Strength Threadlocker Blue' for the bolts (use your favorite brands as you wish!). A friend even let me borrow his scanner tool (Actron OBDII CP9135).
How difficult is this repair?
In principle, the entire repair sounds rather simple: Take everything off to expose the lower intake manifold, clean everything, apply new gaskets, torque intake manifold down to specs, done!
In detail, replacing the intake manifold gasket is very time consuming.. Replacing the gasket is a breeze, but to actually get to it, that's the big deal! There are a bunch of tubes, lines, hoses and wires in your way. Most of the wires have colored connectors and you will have to remember their location when it comes to reassemble everything at the end of your (hopefully successful) repair.
Take as many notes & pictures as you can!
Along the way I took notes, and I mean MANY, very detailed notes. I am not a mechanic, that means that I have removed many items from under the hood not even knowing their names. So I used a lot of simple drawings to describe these items in relation to the ones I already knew (I knew just a few before this repair, but I got better as I dived deeper into this job). For example, I didn't know that the 'device right of the thermostat' is called an 'EGR Valve', so I put 'it' in a Ziploc bag and took it to AutoZone to get a gasket for it, and the guy there was friendly enough to tell me what the 'thingy' was.. :)
I also took many digital pictures, sometimes 4-5 of each step, depending on how difficult I thought it would be to either get to that part, or to put it back together (i.e. distributor).