Yes, you can buy the oil analysis kits on line, at motorchecklab.com, or at any local Cat tractor dealer.
I am 76 years old, so am likely 90+% already worn out, and I certainly am not rebuildable.
My "oil" samples are done yearly, and in a tiny glass jar ( I don't do oil samples on my tractors since I have owned them for a while)
You may be able to find a mechanical thumb that will work for you on E-Bay, or perhaps from Titanmachinery.com.
For a GOOD mechanical thumb (I think the Titans look flimsy in their photos) you might expect to pay at least $800, plus having it welded on your machine.
For a hydraulic thumb it would likely be twice that.
I had one custom made (mechanical), and it cost me $900 installed, I thought that was a bit pricey, but my hoe bucket is very large.
Do not buy the cheapest thumb out there. It may fit, but you will bend or break it!