We're not going to put a number here that we can't back up. What a new door runs depends on the opening size, whether it's insulated single or double layer, how many panels, and whether the opener gets replaced at the same time - and those variables land differently on a 1977 opening than they would on a newer one, since some original openings in this area run narrower than today's standard sizes and need a frame adjustment before the new door goes in.
What we can tell you is that the area's median household income, $113,687, sits close to the broader service area median of $113,750, which is part of why we quote jobs individually rather than publishing a flat rate that doesn't hold up once we're standing in front of the actual opening.
If your opening is non-standard for its era, factor in that the quote will likely be higher than a straightforward swap, because the frame work adds labor before the door ever goes up.