Need Help, Quickly.
 

I drive a 97 Chevy S-10 LS, a few weeks ago the "Service Engine Soon" light came on, my truck has been rumbling and shaking every now and then when driving, the oil gauge usually stays around 60, it has shot up to almost 80 at one point but hasn't done it in a while. Last night on the way home after picking up some drinks for Thanksgiving, I was stopped at a red light and my truck started rolling backwards, I hit the brakes to no avail, shifted into park to no avail then shifted back into drive and hit the gas to go forward to keep from hitting the car behind me.

I've not driven it since, I'm unemployed at the moment so I can't afford to take it to a mechanic or the dealership, yet I NEED my truck to stay working in order to find another job. So does anyone have any clue whats going on with my truck? I thought it might be the transmission but I'm not sure.

Any help would be appreciated and it is greatly needed.

The SES light came on "a few weeks ago" but what did you do about it?

Nothing, as I can't afford to do anything. I thought maybe it needs an oil change, it's now 2 days past due for an oil change, dunno if that matters or not.

A lot of expensive components can go bad from the time the SES light goes on. As for "started rolling backwards, I hit the brakes to no avail, shifted into park to no avail," there's something wrong with the brakes in addition to the transaxle? Have you checked the brake fluid level and transmission fluid level at least? It's probably best not to drive it unless in an emergency.