On a door built around 1990, the spring itself is rarely the only worn part. Cable fraying near the bottom bracket and a tired center bearing plate are common on doors of that age, and if we only swap the spring and leave a frayed cable, you're back to a stuck door in a few months.
The other way this goes sideways is sizing. A lot of 1990s-era builders put in doors sized for the house, not for a catalog average, so guessing at spring tension from a chart instead of measuring the actual door is how you end up with a door that slams down or won't stay open on its own. We measure on site every time.
One honest limitation: if the torsion shaft itself is bent or the drum is cracked, a spring swap alone won't fix the door, and we'll tell you that before we quote the job rather than after.