Thanks for all the replies.
Here is an update on the non-track stuff related to this excavator.
I am afraid this was a very poor purchase on my part. I am really paying dues at the school of ignorance.
The previous owner said they would do maintenance, but I took some money off instead. At least that way I would be sure of the work done and the parts used.
Here is what I have found:
* Engine oil was black. I have an old diesel tractor so I know it gets dark, but this was BLACK. Sample sent in for analysis.
* Final Drive oil was midnight black and stinky as F. 2 of the 4 plugs were stuck, one had the hex stripped out. Samples sent in for analysis. I filled with diesel, swished it around a bit, drained, put in a quart of new oil, swished that around a bit. That is draining overnight and then I'll fill with new oil. No silver sparkle flakes, so there is that.
* Fuel filter / water separator was really stuck in the housing. After giving up on getting the old filter out, I ordered a new housing for $200. Then--since I had nothing to lose--I took the old housing in to the vice, cut the filter out, and after much careful hammering, I finally got them separated:
Cleaned out all the rust, decided all the critical seals were OK (they are part of the filter), put it back together, flushed it good and hooked it all up. So a lot of labor, but at least I can cancel that $200 housing.
* Air cleaner had _no_ inner filter

The outer filter was expectedly very dirty. Replaced both.
* Looked at having the coolant analyzed, but it was the same cost to drain and refill so that is on the schedule.
* I have new cabin filters, replacing them is on the list.
* Have new teeth installed, new side cutters on the way.
* Replaced the hydraulic filter cartridge. The horizontal glue stripes that go around the filter had all come off and were at the bottom of the housing ?!? On the plus side there were no particles in the filter and no sparklies in the oil or on the filter element.
*The rig is cosmetically in pretty good shape and has a decent-ish paint job. The stickers that basically say "hydraulic oil here and "diesel here" were swapped:
I tried to get new stickers and that is when the CAT parts guy informed me that it is a "grey iron", since the stickers are not in english. Sigh.
All this deferred maintenance is disturbing, and I am now thinking that the last service that was done on this machine was done on the other side of an ocean. Well, I have all the maintenance under control and although not pleasantly surprised, I guess I kind of accept that this might happen purchasing from a private party. It makes an ex-rental that has been regularly serviced look quite attractive, in hind sight.