An example of why I don't agree with anyone other than a licensed vet doing vaccinations of any kind.

A vet and their staff are trained on proper storage of a vaccine and they are never removed from refrigeration until ready to use immediately. Vets buy their vaccines from reputable manufacturers and distribitors which always overnight ship with ice packs to maintain the vaccines and put immediately into refrigeration, packages that are not cold upon arrival are not accepted and the company must re-ship them. I don't know how well vaccines are maintained during or after shipping from pet stores and the like.

Also not all vaccines are created equal. Some vaccines do not vaccinate for all the species of some diseases, like Lepto, that may be prevelant in your area, your vet would be familiar with which ones your puppy would need for your area, your pet store probably does not.

As for re-vaccinating, I wouldn't recommend it within at least a 2 week time period. If that vaccine did have some kind of effectiveness then re-vaccinating before the immune system has had a chance to mount a response will cause the puppy to not develop a proper immune response and could possibly cause the puppy to get sick from overvaccinating.