I had one of those Bamar reefing systems on my last boat when I bought it in 2005 (a Westerly Merlin). It seemed quite old at that stage. From what I gather , these are old generation roller units and not as reliable in use as the newer mainsail roller furling systems.
I had a bad experience with a roller main on charter boat just before purchasing, and I removed it prior to our first sailing season and fitted slab reefing and a new mainsail & stackpack.
Since I didn't use it , I can't offer experience of that sort. But if you are nervous of it .... I can say that removing it was relatively easy, even for a first-time inexperienced boatowner with limited DIY experience. I had the mast on the ground anyway, so drilled out the rivets and I don't recall any problems arising. I think we filled the holes with new monel rivets. I would ask a rigger or surveyor first before doing it (in case there are structural issues to consider), but we sailed her for 10-12 years in some very mixed conditions and never had a problem.
Personally, I would factor removal & a replacement mainsail/stackpack into the offer price - and ask the surveyor to review it and ensure that removal is safe. It will be a negative factor when you come to sell the boat, so try not to be the one to take the hit.