Starter motor change - '93 M900

[Goofle]

Not sure if this should go in 'engine, clutch and gears' as its a mechanical question, or 'electrics' as its a motor. If I'm in the wrong spot, sorry!
I've just got the Keihin carbs in, fitted, engine running and, so far, no fuel leaks. I'm happy! Then the bike stops dead, no electrics at all. Main 30a fuse blown, fuse replaced, electrics now working - apart from the starter. Investigation shows the motor failed, and is totally open circuit. How big a job is removal and replacement please? Is it likely to be something in the motor that I can sort easily (worn brushes for example) or should I just get a new motor ordered?

Thanks all!

Ps it sounded well with the carbs, and seemed eager to rev! I've not ridden it yet however...