Go to YouTube and do a search for big buds. You should get some good videos especially the Welker Farm videos. I myself own a 1978 Series 2 HN 320. Bought it just for a toy but did do some serious field work with it until it got coolant in the oil. Someday it will get a newer engine and be restored. We farm 120 miles from Havre. So Big Buds were a common sight around here.  We had the acreage to justify one back in the day but the problem was they were horribly expensive.  So we made do with a Versatile 950 and those Versatiles were the cheapest 4 wheel drive tractors to ever own and operate.  If you are going to buy one there is no better time then now. They didn't make all that many and I already see some collectors advertising for them and buying them up.

Neighbor bought 1 used "because he had to have a "BUD".. After a yr/2 it LEFT.. When I asked he said " the parts cost per acre were more than 4x what the Versatile's parts  cost per acre was". 

I looked into buying a Big Bud in 2000 to pull an airdrill.  I only needed 350HP, and the smaller model 20 year old Big Buds were competitive in price to 10 year old JD and CaseIH 4wd tractors.  I decided against the Bud because they didn't have the hydraulic pump capacity to run the fan on an airdrill, and even at that time parts were getting expensive and hard to get.  I can't remember what engines you could get in the smaller ones, could have been Cummins 855, Cat 3406 or a Detroit 2 stroke of some kind, so parts for those are still easy to get, but when you move up to the Cummins KTA1150, engine parts get hard to find and very expensive.  I also recall talking to someone in Havre that said one was tore down in a shop and sat for 6 months waiting on a part for transmission (made by Twin Disc I believe).  That was a deal killer for me.  I think owning one as a collector would be fine, and putting 100 or so hours on it in the fall would be fun, and if it goes down, no big deal if it is just to play around with and not the primary tractor.