Roller replacement is one of the more doable DIY jobs on a garage door, provided the door is down and the opener is unplugged before you start - the risk isn't the roller, it's forgetting the door is still under spring tension while you're working near the bottom bracket. Loosen the bracket, slide the old roller out of the track, and the new one usually drops right in if you've matched the stem length correctly. Where people get into trouble is the top rollers near the spring assembly, or rollers on a bent track section - forcing a new roller into a track that's already warped just repeats the wear pattern. If your door was built close to 1959 like a lot of the stock here, the stem length on the original hardware is often nonstandard, so measure before you buy rather than guessing from a box label. We're happy to talk through what you're seeing on the phone if you want a second opinion before you commit to doing it yourself.