Swapping a garage door yourself is possible on paper and a bad idea in practice, especially on a house this old. A torsion spring under tension can break a hand or worse, and if the hardware is original to a 1970 build, you have no record of how many cycles it's already absorbed or how close it is to failing mid-removal. That's not a risk worth taking to save a service call.
What you can reasonably do yourself: measure your current opening's width and height, note whether the door is single or double, and take a photo of the existing track and spring setup before anyone comes out. That gets a quote started faster. The actual panel swap, spring tensioning, and track alignment on an opening this age is not a weekend project, and we'd rather say that plainly than have someone call us after a DIY attempt has already gone sideways.