A dryer should last for 20 years or more. An used one on craigslist should not exceed $100. $200 or $300 could get your a pair with washing machine.
If it is the belt, replacing it is not difficult. Put on it on the last step requires some tricky try and fail, but overall it is simple.
http://www.parker-house.net/articles/DryerRepair/DryerFix.php
http://answers.yahoo.com/question/index?qid=20081104065920AAt6Vyc