Speaker/Amp Question

Hi all. Im a 3 year guitar player switching over to bass. Partly out of necessity, and partly just wanting to broaden myself. I am also a poor community college student.

I was wondering, if i were to purchase a twelve inch bass speaker, and put it on my 12 inch combo in my bass amp, are there any forseeable problems. I know id have to match the ohms. But beyond that im clueless to the bass amp world. And perhaps where to purchase speakers? (Musicians friend seems to be lacking).

Also, for the time being im going to be using a pick because thats what im most proficient with, but any guides or suggestions on finger picking technique or any suggestions at all for me?
Thanks
MC Electric Money

 

Im real sorry. what i meant to ask was could i put a 12 inch bass speaker and remove the 12 inch guitar speaker and have in function resonably well.