If your A&P is "very much familiar" with Skymasters, I wouldn't worry. He'll know what items need attention. If your A&P hasn't seen many Skymasters, I would consider flying in a Skymaster expert to help with the prebuy. A 1,000 euro expense could save you 10,000.
If you're really stuck, the book "The Cessna Skymaster" has a very basic (17 item) pre-buy checklist.
https://skysmith.com/product/cessna-skymaster-book/ It's copyrighted so I won't repost it, but point 17 is "Have a good mechanic that
knows Skymasters do the prebuy inspection."
"if icing condition prevails ,stay on the ground Or take Easy Jet Flight" - good idea!