You will find the process of rennovating your Overlander less daunting if you break the various needed updates into manageable mini-projects that will permit you to use the coach between projects. I followed a similar process with my Overlander when I acquired it in 1995.
My first project involved a safety inspection that included determining that the axle still had some life left (it now needs to be replaced), but the brakes and shocks needed to be replaced. Initially, there wasn't evidence of immediate concerns with rear end separation but the outrigger nearest the refrigerator had to be replaced. A new power converter and a replacement water pump had me on the road for several years - - about three years.
The third year, both the water heater and furnace had to be replaced, but I was still able to continue traveling. I never really had the Overlander out of service for any great period of time. My restoration/rennovation was spread over the years of 1995 through 2003 so the expenditures each year were relatively controlled. The two biggest expenses were in 2002 and 2003 when I had the interior refurbished by Fowler RV Interiors
and when I had the exterior refurbished by P and S Trailer Service
- - each of those expenses were in the vicinity of $5,000.
I haven't regretted sticking with my Vintage Overlander as it is a wonderful compromise between size and towability. In addition to that, it has a floorplan that isn't available in the more recent Airstreams - - I considered a new Airstream before purchasing my Overlander, but the modern Airstream bathrooms were just too small when compared to the comfortable bathroom in my '64 Overlander.
Good luck with your investigation and rennovation!