I wouldn't be surprised if your local dealer still carries NH parts in some form or another... If they sold the tractors for a lot of years and there's a parts market out there... they're going to try and fill it somehow.
If they're not selling parts... tract down another dealer. Any I've ever dealt with were more than glad to take a CC number or CNH Capital card...then drop your parts in a couriour bag overnight. It's a way of life 'here'.
As far as the tractor goes... if it's 2WD I would NOT put a loader on it. If it's FWD I might... if I could find a cheap enough loader. 1600 is an old tractor today in terms of compacts. I would not want to get too much money tied up in it myself. If it ever had a major failure it will cost mor to fix than it's worth if it can be fixed...