Appointments+ payments

I have a client (attorney) who would like to make appointments and have her client pay for them with a credit card. It looks like maybe I need to setup MarketPress (which I haven't done before), Appointments+, and Stripe to get that to happen - is that right? Do you have a KB article how to get all that going and integrated? Also, what happens if you guys raise the price of membership and I cannot pay for renewal - can she still use the plugins? Thanks, Ed