Yes, upgrading the HD is pretty easy thanks to the outstanding Empeg FAQ.

I would try to get my hands on an Empeg first if I were you. And, if you've got the patience to wait for it, you can always buy one of Patrick's Empeg Tuner kits.

$500 for a 10gig Mk2a should be do-able, but 10gig Empeg's have become rare.