Two things, it may need a really good cleaning of the dryer itself and the vent line. Especially if you use a plastic or corregated vent - those both trap lots of lint and end up costing much more and lengthen the drying cycle times. Depending on how it is put together, you may need a long brush, an air compressor, or you may be able to poke things out or vacuum the lines. Dryer lint is a major cause of fires, and is a likely reason you may smell something buring.
Regarding the thumping...open the door, and push up on the dryer drum near the front of the dryer. If it moves much at all, it probably needs a new idler wheel(s) and bearing assembly. Last time I needed one, it was less than $10. On my old dryer, it was an easy, fairly quick fix since the front cabinet face was designed to easily come off. One bolt, the thing was off, stick the new one in, adjust the play out of the system, tighten it back up and you were done. If it's the main bearing rather than the idler wheel(s) (there are often two), I've never replaced one of those. the other thing it could be is the drive belt is breaking up, and that's fairly easy to replace as well.
There isn't too much else, but with the cover off, it should become fairly obvious. Course, you could always pay a repairman, too!