Having watched the sausage video thing I think I should be able to just hammer the gear box and crank free of the casing. Is that right?
No, don't do that.
Strip the gears off first, large circlip and try to remember what way off they came.
Then tap the shaft whilst being careful not to damage the selector, which is like a Lambretta one, wiggle and tap and wiggle and pull (in that order sort of).
I am not to clued up on the various kits for Smallies, I like the DR as a basic upgrade, Malossi as a faster but useable kit, the one I am doing at the moment I will be leaving the 90 top end on (I think).
The Smalleframe forum is ace for advice, but some of the guys are so clued up on the ins and outs, it goes way over my head
Shaun.