Check engine light - Lexus rx300

Lexus rx300 I just had the oil changed they told me I have 2 oil leaks b/c oil was leaking from the oil pan and the head gasket. Maybe (i think) and it would cost 800 to be fixed. He also said that I MAY need a new timing belt. He said I could drive it without these problems being fixed I would just have to keep putting oil in it so that is what I intended to do - however my car has almost 300,000 miles on it but it has been very well maintained however now - first it was the shaking when idle, then the check engine light came on. It drove fine once it was going but when ever I would stop it would ****. Then I was driving all of a sudden I heard a wierd noise and my Rpm's went up really fast and I was hardly even touching the gas. Then it stopped moving altogether so I sat idle for a few minutes and drifted into the parking lot where its still sitting.