the hand brake lever/ratchet would come as a complete unit i would have thought
(it's worn,and has no relation to the fluid leak),but should be pretty easy to
change.
as Kenney says, if a sensor is faulty, it needs changing for a sensor that isn't faulty,
the fluid leak could be a pipe,as you say, but it could also be caliper piston seals
which would probably work out cheaper to renew than to clean and re-seal,going on
labour rates these days.
hope you get it sorted without breaking the bank,
please let us know how you get on,
regards,
stewy.