I had all the same worries as you are posting on a plane I purchased a couple of years ago. All my worries were unfounded. The engine had a few hours on it and sat in the hangar for 11 years with nothing done to it. I did put a soft start on it, had to chase down an intermitent ignition (broken wire) issue. but other than that, the engine is as good as new. I recently removed the pistons and installed the 105 HP Zipper kit on this particular engine. It literally looked like new inside. The engine sat in semi humid area (northern MN) in a hangar that was 50 feet from the lake, so basically wet climate.
I also read and worried about the hose replacement, I took most of them off and they looked like new so I didn't bother replacing them. Just me, I'm a cheapskate!!
Even at $5000 for it you are stealing it! As mentioned, I have seen mid-time engines selling for $10K. Unless the seller is some old guy that doesn't know what he has and is getting taken advantage of, that price is a steal. Just watch any of the Barnstormer or TAP ads and any engine under $10K is quickly snatched up. A new one (zero hours) even of '95 vintage, priced at this price, would not last long in my opinion. I have been in this game for 30 years and have met my share of shiesters and scheemers, buying and/or selling items, but for a new engine at that price you better move on it before someone else finds it and offers the seller market value. I know several guys would be that guy if they knew where it is. I have 3 friends that have been looking for an older low time 912 for under $10K and they have been searching for nearly a year. When one is found they either find it is already sold, a deposit on it, or they were hoping for a better deal only to lose out. All opinion!!!