I have 1 LaserJet IIp and 3 LaserJet IIIp printers.
None of them are really 
    Trash. They were unusable when new, they are unusable squared now.
  I could always use an extra printer, so I have to
decide if I should get
 them working or just dump them and get something new when I really need
 it. 
    If it were a full III, I'd tell you to keep it, it is still a good
printer. But IIIP? Trashcan!
  Is there a source for GOOD toner cartridges? Google
finds a bunch of
 cartridges, but how many are junk refills? I am willing to pay for good 
    Make it yourself :)
  cartridges, but I can't tell good from bad. Are
feeding parts available if
 they start to pull multiple sheets, etc? Are there reputable sources? 
    There is a smal solenoid that locks one of the paper pull rollers. This
solenoid has a smal foam disk on it that when gets old, it locks the
solenoid closed and creates all types of paper feeding problems. It is on
the right side of the printer, I believe you can see it with the door
opened. Replace the foam disk with something like electric tape and you're
set.
  I know these have a good reputation generally, and I
used one for a long
 time in the '90s. 
    I just hate them :)