if the bolts are not rusted fused onto the metal bush, it'll only take few mins.
u remove the center heat shield then the selector rod from gearstick & gearbox
push out the bush, wipe clean with wd40 and wirebrush the rust off.
can also push a flathead onto the middle groove of the plastic bush and they pop off the gearstick/universal joint in 2 pieces to clean.
check if the riveted bush moves ok. if its free then u can leave it. if its also stiff then grind the rivet apart and clean that bush too.
regrease and reassemble.
always a good idea to clean all threads with tap & die tool then copper grease before fitting.