Forget the rear 'Speeds' change^^ stick with what you have . got 9 0r 10? stick with it , Repair- replace without "upgrading".

Cranksets just have chainrings 2 or 3 of similar target market IE road Triple to compact double also for Road bikes should be doable .

you have to buy all the tools for the job too. unless your local cyclists have formed a CoOperative.