You should be able to keep tabs on his nails pretty well from him white nails; black nails are always more difficult, but you'll get a bit of sense from the white nails, and you can just be a bit cautious with the black ones.
If you're really uneasy about it, you can usually also get it done at a vet's office (technician appointment) or pet shop (call first). Depending on the services offered, many might be willing to show you how, as well.
Young piggies have little needle nails ... they get a bit thicker as the piggy gets older.