Our 1992 Trane AC was still going strong until we had it serviced last year. Wondering if my HVAC used wrong refrigerant?

Trane TXC031C4HPA0 is original to our 1992 house and always did ok, but it's a 2.5 ton unit and a bit undersized. I've kept it going with new fan and capacitors over the years but it never needed refrigerant until recently.

It wasn't cooling well last summer and we had it serviced. Tech said it was an R-22 unit and added a couple pounds. Total cost $500. He came highly recommended but is an independent local guy.

It survived last summer but would barely cool when we tried it for the first time last week. Called the same tech and he found oil around the coil and lineset on the outside unit. Diagnosis - replacement, but recommended keeping our furnace (I agree with that part, furnace is solid old school trane.)

Here's the problem - I ran the model number on the indoor unit and it comes back as an R-410 model. Assuming that's correct, did the tech either lie and fill it with R410 and bill me for R-22, or did he screw up and put R-22 in the unit? And did that kill it? Would it even have run with R-22?

We manage several properties and have had nothing but frustration with HVAC companies. Thinking I may just tackle the replacement myself. I've done mini-splits before and I have equipment to vacuum everything down, etc. It's just out of my comfort zone.

Another note - he just wanted to reuse the old lineset without flushing, which I'm reading is fine for R410 to R32, but not for R22 to R32...Red flag?