I am a DIY guy and want to fix up this trailer. I have never owned a trailer before but look forward to be apart of this. I would love some assistance please!!

This 64 Avion was a work space for a construction site and needs a remodel. I looked over the frame and exterior and it looks good but the interior needs work. The Veranda area was ripped out, the kitchen, Frig, and Bath are there but don't know what works. they put a swamp cooler in the roof and think it leaks so would like to put Air/Heat. I would love feedback on What type and size? I don't know what shape the electrical is in and if I should replace it? I would like to put Flat screen/ Sterio as well.
Anyway I look forward to your feedback and forward to the build!