High RPM problems with my Cadillac

Question type: Maintenance & Repair

My cadillac deville is having engine problems. It was having trouble starting (I would have to hold
down the gas pedal and keep the engine idling so it would stay on and not stall out). I took it to a
mechanic and it decided to work fine for him, but he said he cleaned out the throttle body and reset
a few computer codes. After I got it back, I noticed the car seems to jump when I slow down and the
car shifts into 1st gear, but it happens at random. Over the last few days though, the engine has been
idling at higher and higher RPMs, usually above 1000 when I'm stopped. Today, I was driving back
from work, and on the highway it was staying close to 3000. What is wrong? What can I do to fix it?
Can I take it back to the mechanic and have it fixed? Because it wasn't running this bad before he
worked on it.