HP DeskJet 2652 - still on warranty

I bought a HP DeskJet 2652 last August. Was working fine and then the gremlins came. Got it all fixed up and again the gremlins. Won't print but I can print a test page but only in Red and Blue. (Ink has just been replaced). The scan is possible but the quality (regardless of the setting) is all the same and okay (at best). Was very good at the beginning. It is a cheap machine $30 but still under warranty. Walmart won't take it back.
Never done this before...so what will probably happen?

If it makes any difference it was paid with a credit card that doubles the warranty. Thanks.