Wallace took his computer into a repair shop, and now he's concerned that they could have put monitoring software on his computer. This is a legitimate concern, and often times it happens remotely with people calling that claim to be from Microsoft or something. If someone has physical access to the system, though, all bets are off. Taking a computer into a repair shop is an absolute act of trust. There's not much he could do about it, though, if he needed to bring it in. There's no certification process or national organization of computer techs, so he'd just have to trust them.
One thing to try before taking it in for repair is wiping and reinstalling Windows first. There are bad things that can be done that would survive a reformat, though, if he wants to be really paranoid. The best thing that he could do is make sure to check the Yelp reviews and make sure its a reputable place.