this is a real pain, I can tell you.
I fiddled four weeks to make my Lexmark X125 work partially. I almost went back to Windose.
The Lexmark p3150 is an all-in-one generic printer and you´re pretty lost with it. Concerning the Canon s450 you might find some hints here:
Shouldn´t be completely hopeless.
How to install that driver? You´ll have to plough yourself through the linuxprinting.org webpage in order to get an idea.
It´s a mess for newbies but I didn´t find a faster workaround either. Prepare for several night sessions and an ill-mooded spouse. (If you have one.)
If money´s not an issue, sell the printers on ebay and get yourself a postscript printer. Saves app. one hundred hours and several grey hairs.
Don´t give up. Always be aware that at the end you´ll be FREE!