The pictures show a 2000 DGC - where the heater box is insdie the dash - I bet a 2003 is similar.
full story here: http://www.gearheadgospel.com/vanfix/
I would certainly check fuses and the heater controls before you "dig-in".
The AC was only working on high speed so I replaced the resisor and it burnt up the new one in about a week. Everything I have read says to replace the blower motor. Was looking at it last night and it looks like just might have to take glove box and the cover which is held on by a couple of screws. Does that sound right?? Thank you once again for all the help!!!