transmission problem

i have a 1997 pontiac montana transport. the problem began about 6 months ago. when driving along about 60 mph with the cruise on all of a sudden the engine rpms whould start to rise as though the vehicle went into neutral. had to pull over and stop turn the vehicle off for a second then restart and the vehicle ran and shifted normally. as long as i drove the vehicle at moderate speed 5o or below it does not do this. next thing to occur was a shifting problem. if you drive normally the vehicle would rev up when shifting to 2nd gear and would not shift unless you let off the gas. if u baby it and accelerate real easy it shifted ok. My wife went out the other day and put it in gear and now it won't go at all.
I have checked all the usual things fluid level etc. I always work on my own vwhicle so I would rather not take it to a shop. Their only response is that it's shot. It is a 4T60E model trans.
Thank you

Unfortunately, I have to agree with the shop. The transmission has gone out and will need to be rebuilt or replaced. Find a reputable shop to do it or purchase another one and replace it yourself. Sorry for the bad news.