I don’t usually keep vehicles very long, but I have had a 2017 Ford Explorer XLT 4WD for a few years, and I am trying to keep it for 3+ more years if I can. It currently has ~69,000 miles, and I have never had a transmission flush conducted on it. I change the oil, cabin air filter and engine air filter regularly myself.

My question is if a transmission flush is necessary for longevity, and what is a reasonable cost for that service?

Alternatively, is this something that I can do on my own fairly easily? I have heard that the fluid proportion can be tricky to get right, which is my main concern.