I am having literally the exact same problem on my 7510 and came here looking for help. I've got it partially disassembled and hope to get the feeder assembly out but it looks like a pain in the @%^ to get to.
The rollers on the paper feeder turn but very weakly and I can hear crunching sounds but the exposed gears seem to be OK. I'll post more once I have done more of a thorough investigation.
Basically at this point it's fix it, or get a new printer so I have nothing to lose.