Really, any trailer of that vintage will need systems replaced at some time. Figure on... (from my experience with our 26ft Argosy)
1) AC - eventually they go... but run great until they die. (500-$700)
2) Fridge - check for an ammonia smell or yellow dust on the coils - this means the ammonia has leaked out.... the fridge will have to be replaced ($1000 - 1200 - but there are those who rebuild newer ones for less).
3) Univolt (converter from AC to 12v
DC). About $200.
4) Heater (just did mine, I highly recommend you replace it for your safety). $500-600.
5) Hot water tank - just use it until it leaks. $300.00
I stripped our paint off. Aside from the steel endcaps on the ends, it looks great. You might be able to strip off the peeling paint on the top and just Krylon paint it to match.
Fun working on the trailer and using it - priceless!