With that mileage, I'd be more concerned about servicing the supercharger.

I believe the story about the first transmission oil change at high mileage is mostly for the automatic transmission which has fine channels and small ball valves that may be sensitive to small contaminants that may break loose from an oil change. The torque converter also makes it difficult to replace all the oil in the transmission.

In contrast, the manual gearbox is an open case with exposed gears and bearings.

You should be fine, but you can also try NAM as Willie suggested.

Join and ask in this group. We are mostly classic minis here. https://www.northamericanmotoring.com/forums/

Hello, I just bought a R53 (2005 S).  It was from a 1 owner who is a car guy and keeps his rides as mint as possible.  Even thou the car runs and looks great; I am going over it to make sure everything is as it should be.  So, it has 201,000 miles on it and I don't know if it has ever had the fluid changed in the Manual Transmission. Am I good to change it or will it cause any issues? I have heard on some cars that if the trans fluid has not been changed ever 100,00 that changing it may cause the trans to start slipping, I don't know if that is true or not.