Hi scotty, I want to thank you for your years of helping people out. You genuinely care for people and there money. I would like to ask you if it is safe to change the fluid in a high mileage manual transmission that has never been changed before 😀
You put your post in the wrong place, the length-limited title meant for a short description, so it was cut off. You may want to post your remaining text as a comment here. (Text moved.)
You also left out some important information.

In general the oil in a manual transmission can be safely changed at any time.
Fresh oil in a manual transmission can only make it work better and last longer.
Yes. Works differently than automatic transmission.
FWIW, I have had my 1999 Honda Accord since the beginning. And I never changed the manual transmission fluid until the 200,000 miles. And when I did, it turned out fine. Had I known my about cars, I would have changed it sooner.