1977 dometic refridgerator

i have a 1977 airstream overlander. my fridge is a dometic and it doesn't work very well. it does not work on 12 volt and it doesn't work on a/c. the freezer will try to work on gas but the fridge portion doesn't do anything. also on my fride some of the control nobs have been stripped. the control rods are damaged from the previous owner using pliers on them. they are difficult to use and extremly hard to figure out what position the control is in.
I have tried every combination possable to get the 12 volt and a/c to work, but nothing happens. i have all the original nobs but they are stripped as well they only work as guides to temp and fuction positions.

now to the question is it more cost effective to replace my fridge with a new unit or repair my exsisting fridge, can you get parts for older dometic fridges?
please help.