You guys are really going to enjoy your 550's. Here's a link to a good article found on the left side of this website...Research and Info, Artices, Maintenance, Oliver 550 purchaser's checklist. I didn't write it, but it sure was helpful.
Order yourself an owners manual - they are filled with all the necessary info to maintain the tractor, lots of detailed info. Also a Service manual if you intend to do more work. Have fun.