just a note about the xclamp fix... it's not permanent. it gives you maybe 6 months of playtime. i repaired about 5-6 360s early on when the xclamp fix came out. however they all died again after a few months. and subsequent attempts to re-fix including cleaning and reapplying thermal paste did nothing to help.
why was the dvd drive replaced? is it a hacked drive? barring anything questionable (hope you're not pirating), you can probably still send it back to MS despite the voided warranty. a few people including myself have sent back warranty-voided machines and received back a fixed one.