A decent new 26" wheelset will run you $150 on up. You may be able to get decent wheels for less by buying a used bike (e.g. on craigslist) for its wheels.
It sounds from your post as though you probably don't yet have the skills to identify a decent wheel or do minor fixes on a wheel; I'd strongly suggest finding a good local bike shop and have them take a look at your bike and at least give you an estimate on the wheels (maybe yours are fixable, maybe not) and on the condition of the brakes, powertrain, and frame (especially possible safety issues!).