8820 Deeres, what are they like ?

We only have a fairly small operation and need to replace our 37 year old harvesters (2 of) with something a bit faster. We are currently looking at an old 8820 JD Titan 2 and my brother and I are wondering what the differences are between an early 20 series and the Titan 2, or is it just a flash sticker on the side?
The machine we are looking at is supposed to be a 1989 model but I have no idea how to verify that, also do 8820s have any major design failings or is there anything that gives trouble we should be looking for. We have had a look but it just appears to be in normal order for its age. This machine has 4000hrs up so its not new but appears to be in good order, no rust in frames or anything and paint in good order so its not been outside much. We can't see anything other than that its a bit old but we would probably only put about 120 hours a year on it.

What do you blokes think, is it worth mucking around with or are they too fragile at high hours.
Graham, from Western Australia.