Does the trackpad have less travel, or a less clear and crisp click? If so, I would go the battery route first. If it does not show these symptoms or just doesn't work at all, take it to an apple store. It is probably the trackpad itself. This can be replaced at home but a trackpad issue could be many different things, so I would take it to an apple store first.
There should be no issue. Repeatedly erasing/wiping the drive can eventually shorten its life span (especially in the case of an SSD) but not enough for you to even notice. So in short, there isn't much of a problem at all.