Find out if the new owner will cover the old shop owners warranty. "Oh Sure" isn't an answer, ask the new owner yourself.
If you can't get a promise from the new owner, wait until they take over the shop and sell old inventory
the 8900 is a great machine, but like all computer machines today it will not last your life time. technology changes too fast and it isn't long before you can't get parts, particularly motherboards. Take the long view vs. the short view for your purchase.