Chevrolet: Condition of oil - over heating, blown head gasket, intake manifold gasket

Question
1995 Chevy Corsica 3.1L

Background on car-----
I drive about 2,500 miles per month for my work, mostly highway.  Had to replace the transmission in December, and put on an additional, smaller radiator (so the transmission fluid doesn't mix with the coolant?).  My last oil change was about two weeks ago and I assume they topped off all the fluids.

Current problem-----
Last week I noticed my car performing rather poorly.  The next day my car still performed poorly and the temperature gauge was all the way up and the light came on.  I was 100 yards from home (it had overheated just as I was driving by my residence from running errands) so I turned around and parked it.  I had to leave right then to go out of town, so I got a ride from a neighbor to work and had no time to even pop the hood to see what the problem might be.

When I got back to town two days later I put some new coolant and water it.  It took a full two gallons and showed no signs of leaking.  I'll point out now that I had a problem with my low coolant light always being on, even when overfilled, so I disconnected the sensor.  Because the temperature gauge always worked, I just kept an eye on it that way and getting my oil changed every five weeks meant it would be topped off regularly.

This morning I checked the oil.  The stick shows that there is way too much in there, but that might be that it is just sticking inside the tube.  The really big concern I have is that it is a light brown color with the consistency of thin gravy.

Questions-----
Are these problems related?
What is the cause?
Is there even a chance that it is a simple repair or did I crack the engine causing coolant to get into the oil?

Thank you for your insight.

Michael R Rivers

Answer
There are several posibilities to the cause. Either the intake manifold gasket is cracked and coolant is leaking into the oil internally (very common), or you have a blown head gasket (somewhat common), or you have a cracked cylider head or block(kind of rare).
None of these repairs are easy for the do-it-yourselfer. There is way to much involved for me to tell you how to diagnose the problem and there are alot of tools required to test the cooling system that you probably would not have. Your best bet would be to tow it to a shop to get it diagnosed by a professional.