A new door install isn't a weekend project, and the age of Cameron's framing makes that more true here, not less. A torsion spring under full tension can put someone in the hospital, and that risk doesn't go down because the house is older - if anything, a jamb that's shifted over 85 years makes it harder to get the track plumb without the right jacks and levels.
Where a homeowner can reasonably do their own work: weatherstripping swaps, tightening loose hardware, lubricating rollers, and keeping the track clear of debris. None of that requires touching the spring or the opener wiring. The honest answer on installation itself is that the opening has to be checked and often corrected before a new door goes in square, and that's not a job suited to a Saturday with a borrowed ladder.