I have an 82 RR. 265000km.
I've always used engine oil in the gearbox - never a problem- 20w50. Stiff gear change might be clutch cylinder(s) giving a bit (master or slave) I've changed both once now.
If brake pedal is going to the floor you can check the obvious things like swelling flexible hoses or leaking fluid, or needing bleed - but here's one that has happened to me twice - master cylinder seals go. And there is no outward signs - fluid just stays inside.

