Hello-
I have a 2001 Nissan Altima GXE and I noticed this past Sunday when I put gas in it, the "Service Engine Soon" light came on. I took it to my mechanic today and the initial test from their electronic machine says it has something to do with the transmission. They can't pin point the actual problem yet without doing more diagnostics. Anybody got any advice/information? The car only has 61,000 miles on it. Am I looking at major bucks here? Worst case scenario? Best case scenario?

I'm a bit leery that he could say an "initial test points to" the transmission.

I've never heard of "initial tests". The diagnosis involves hooking up a computer to the car (in my area usually around $70.00) to tell you what the problem is.

Make a few calls around and ask them what their diagnostic for the cause of that light costs.

Try the dealer first.

Take the best price from a reputable mechanic. You'll then know for sure what the problem is and decide from there what to do... and whether you feel like you need or want to fix it at all.

Make sure the gas cap is on tight and sealing if that isn't it try replacing
Gas cap, if it fixes it you didn't spend a lot of money.