The John Deere is a hearty engine if it has been maintained. Fluid analysis will give you lots of information.
Per parts, do an internet search on your engine to locate parts dealers.
Per other parts..... get up a list of pumps, nnodles and go internet hunting. You did not specify the year in but, I doubt if you will have any problems.
There are lots of GBs out there to abandon the parts.
Find a GB forum and post you concerns and you will get loads of information and recommendations
The meek will inherit the earth but, the brave will inherit the seas.