If the you are not getting any air/heat then the blower motor is probably toast. Should be able to pick up a whole used assembly for about $75 or if you prefer to pull the assembly apart you can get a new motor for around $100-120 on ebay. As noted above by samblaze, it is a simple replacement, should be no more than an hour for an experienced mechanic. Once you've done it 2-3 times you should be able to do it in less than an hour without any problems. The other possible problem would be the transistor as noted by dgandul, the normal symptom being the blower only runs at high speed. It is there next to the blower assembly and held on by two screws/bolts.
Here are a couple of reference pics:
Blower assy:
Transistor:
