1998 Oldsmobile Cutlass Coolant in Oil - Intake Manifold Ga

1998 Oldsmobile Cutlas
V6 3.1L
approximately 80k miles

Failing intake manifold gaskets on both heads. I plan to repair the car myself. I've done many car repair jobs, but none of this magnitude. I don't have the money to pay to get this fixed, so I have to attempt this myself.

Background:
Car was losing coolant for a little more than a year. I had to put coolant in about every other month. The car was not driven very much. Maybe less than 7K per year. The big failure occurred when getting onto a freeway and noticed a considerable loss of power and white smoke from the exhaust. The car was driven for about another 2 miles and then stopped. The car sat for about an 1 to 1.5 hours and then driven about 1.5 miles when I decided to pull over. Not sure if I ran the car hot, but I beleive that is when I would have pulled the car over and stopped. I dismantled the upper and lower intake manifolds as well as the heads. It appears that only the lower intake manifold gaskets failed. Coolant contaminated the oil, but it appears that oil did not contaminate the coolant. The car has been sitting for a year now and I am planning the repair now. I have a Haynes manual that I used to dismantle the engine and plan to use for reinstall procedures. I've read as many posts as I can to find my answers, but could not find any to the questions below.

Side Comment:
A year before the car became undriveable, I had the car at a GM dealership, where my wife was working at the time, to replace a bad camshaft position sensor. One of the three attached wires was broken at the sensor with some of the sheathing melted. I thought this may have been caused by leaking coolant. Anyhow, we told them about losing the coolant and they could not find anything wrong or any leaks. I checked my invoice for the services performed and there was no record of the losing coolant check.

Questions:
What parts should I have checked for damage? By myself or a machine shop. I plan on having the heads checked for cracks, but is there any other part that should be checked by a machine shop also? Such as the lower and upper intake manifolds.

Should any internal parts be cleaned, such as lowering the oil pan and cleaning coolant, if any at this point, off the crankshaft and other parts? If so, what should I use to clean? I was told to use diesel fuel by a mechanic, but I thought that I would just use a brake cleaner. Once the engine is back together, I was also planning to run the car until it gets hot and then do an another oil change.

I planned on replacing all gaskets. What brand or type of gaskets should I purchase for replacement of original?

Do I need to use some type of silicone on the gaskets?

I have been unemployed for several years now and don't have a lot of funds for this repair, but I am willing to make an investment in time and money if I can get another 25-50k out of this car.

Any additional help or tips are appreciated.

Thanks in advance.

Sam