Oil analysis would tell % of gasoline in oil and give a good idea of the "oil washing". Needs a lot of tests; compresssion, leak down, boroscope, wire trace, before condemning the engine. I think it's worth contacting a vehicle transport company and getting it out of there and off to Continental Imports or MB Autowerks or Bergworks. Best $1000. you'll spend on it. eBay sellers transport cars cross-country all the time; one of them will tell you who to use for transport of a high end vehicle.
The Golden Rule
1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)