99 taurus wagon reving high

My previous car's engine blew about 2 weeks ago while I was out of state and I had to replace the car quite quickly. I purchased a 99 ford taurus wagon with 48,000 miles on it. Everything was fine when I test drove it. Now that it's 2 weeks later and I'm home in a different state I'm having some problems. First I hear a squealing noice almost constantly from the rear brakes. It shouldn't be that the brakes are going because the car was inspected before I bought it. Second and my main concern is sometimes it feels as though the car takes off by itself. A few days ago I was approaching a hill around a corner and it sounded like I was pealing out. I think I left skid marks. The car seemed to jump and take off. Occasionaly, not always I'll be driving along and it feels like I get a burst of speed without stepping on the gas much. Just tonight I put it in park and it started reving really high, the tachometer went from 1 to 4 almost immediately, I turned the car off before it went any higher. I'm hoping this isn't anything costly since I didn't need a car payment in the first place. Please someone tell me it's not the transmission or something really wrong. I don't know much about cars at all and I need help. Thanks ahead of time.