95 Pontiac Transport Van not working right. HELP!?

[Rebecca]

I have a 95 Transport Van. 3.1 L engine. Roughly 126,000 Miles. Runs Like Hell. It accelerates badly (I am afraid to take it on the highway because it takes about 5 minutes to make it do 65mph) , and most of the time I have to take my foot of the gas to get it to shift. When it does shift and I take my foot off the gas, it will either shift right or downshift. If it downshifts, I can put my foot on the gas again and sometimes it'll go right back into the same gear it was in again and instead of shifting up like it should, it'll act like it is not in gear at all and it will when it finds the gear, sometimes it will slam into the right gear. Needless to say that is just highway. It also has a noise underneath the resembles a rattlesnake rattle whenever I am hitting the gas. If I slow down, but not slop all the way and then go right to the gas again, it will downshift slowly and jerk the vehicle slightly. Not always but most of the time. Also if it has been running long enough to get warm, and I turn it off to run into a store for a few, It starts, then stutters, and stalls. I have to rev engine upon start to get it to stay running, but is even more sluggish than before. Also, it DRINKS gas, like no other! I can smell the gas, and I can smell burning oil and burning antifreeze inside and out of the car, but I check the fluids very frequently and I find them full. There is no smoke out of the tail pipe, there are no check engine lights etc. One last thing to add, sometimes the temp gauge goes up, not to the red area, but close, especially at idle after being driven a while, but when I hit the gas to go, it goes back to slightly above normal. Any idea's on how to fix this heap? It is all I have and I have two small children that depend on this van in more ways than one. Thanks for reading!