Send out oil samples. Saves a lot of guesswork. Only works I imagine if that haven't changed oil recently.
We recently bought an excavator, and tested hyd.& engine oils.
Both came back well with no abnormal amounts and currently have put on 400 hours with out an issue.
As you probably know, There are measurements you can apply to tracks and rollers to get exact % of life left underneath dozer. Probably get from dealer.
Once dozer warms up to operating tempature, assuming it's a power shift, see how she pushes into piles, and how each gear does under load. Watching for any slippage in gear. On a dozer that new, probably won't have any issues.
Good luck