is it better to have a puppy dewormed professionally and diagnose what kind?

Yes take it to a vet. They don't sell everything for all parasites over the counter.

If my dog had worms I'd go to a vet. That said if you're short on money I'd be careful about the research you do. SO see if you can find actual reviews and testimonials on the products you're interested in buying.

It's always better to consult a vet, but if you do it yourself make sure you get a wormer with hookwormer in it a lot of the OTC don't have it, and a lot of puppies die from having hookworms and not being treated.

As a vet, I say go to the vet :)

Well.. otc is risky.