Please read
Guinea Lynx :: Breeding and
Breeding Guinea Pigs
Risk to the female and babies aside, there is a pet overpopulation problem. No one needs to be breeding.
What are bloodlines really? Can you really tell with them? Personality is not inherited.
Buying and breeding pet stores pigs (who are already highly inbred from their pet mills and whose genetics you know nothing about) is a bad idea. You may be breeding lines prone to heart disease and maloclussion. That's unethical and a lot of vet bills right there.
Pet stores are there to make a buck. They aren't going to talk you out of buying from them.
I'm sure your guinea pig would rather you adopt and save a life in his honor in lieu of risking a poor sow's life.