Caledonia's median household income sits at $91,053, close to the $92,803 figure for the wider area this company covers. At that income level, the math on a door that's into its third or fourth repair call usually tips toward replacement - you're not saving money patching a 1978 door forever, you're just delaying the job and paying for both.
We can't give you a number without seeing the opening and knowing single or double, insulated or not, and what's happening with the jamb. Door size, insulation rating, and opener choice move the price more than anything else. What we can say is that a straight swap on a standard opening costs less than one that needs jamb work, and we'll tell you which one you've got before any work starts, not after.