Rollers look like a simple swap, and on an unsprung bottom section they mostly are - pull the retainer clip, slide the roller out, slide the new one in. Where people get hurt is working near a spring-loaded door with the opener still connected, or pulling a roller near the top section where the cable runs. If your door is original 1982-era hardware, there's a decent chance the track brackets have also loosened over four decades, and a DIY roller swap on a loose bracket just moves the problem. We're honest about the limit here: if you're comfortable with hand tools and the door is off its opener and blocked open, a bottom-section roller is a reasonable weekend job. Anything above the second roller, or any door that still has its original torsion spring, we'd rather you call than risk it.