Swapping rollers looks simple from a video, and on some doors it is. The part that trips people up on a house this age is the stem design - a lot of 1971-era doors used a roller stem length that isn't what's sold at the hardware store today, so the new roller doesn't sit right in the track and starts binding within a few weeks. You can check this yourself before buying anything: measure the stem from the hinge face to the roller wheel, not just the wheel diameter.
We'd also say skip the DIY route if the bottom bracket is involved, since that bracket holds spring tension and is not a part to work on without the right clamps. Rollers alone, top and middle of the door, away from the bottom brackets - that's a reasonable weekend job for someone comfortable with a wrench. Anything touching the bottom fixture or the spring, call it in.