I'll bet that if you typed "Sennheiser ear pads" into google you'd find an answer. I'd do it for you myself but I'm feeling a trifle irritable this morning
Definately possible, I am a techy numbskull and replaced my worn pads (in fact, so worn there was none left) about 6 months ago. Got the replacements from a shop on Tottenham Crt Rd.
Is it possible to get spare cables for those HD 480s?