Hi
it is not simple question to change tuner mate, it is a hard work, aniway change a Nokia dbox2 from cable tv to sat tv i can confirm you is possible, there is a guide of a great teacher around this matter, his name is MACCANICU:thum:
Around your second question i can assure you that Dbox2 can make same like DM........ off course considering his litle resources not all the same...
Greetings
Gianluca