Water punp issues

[hap2]

My car (1987 RX-7) was leaking coolant. I took it in to the local Canadian Tire to get pressure tested. The said it was the water pump. I fear those guys don't tell me the truth just so that i can spend big $ to them to get it fixed when it just might need gaskets or something a lot less serious. Anyway, in this case, I have to believe them.

Anyway, my main questions are:

Is there anyway to check that it's the water pump for sure?

Also, what is the coolant capacity for my 87 RX-7 non-turbo?

Also, where's a good place to get a water pump & also muffler / tail-pipe?

Also, what am I looking at for time to change the water pump?

Thank you very much.