@ PTK: I'm in the same boat with my Commell LS-373 - it has one mini pci, and one mini pcie sockets.
I have a sierra mc8775 card spare, and last night installed the (hacked generic) drivers for it, so windows recognizes it - even 3G Watcher is picking it up, and it's only complain is no sim card.
I will be playing with this the next few days, as it would only be 3 or 4 of the 6 pins (on a sim-socket) that will need to connect to the pcie connectors on the pcie card - should not be to hard, except finding proper points to connect the sim-socket to.
I will check back and post my experience here during next week or so.
If you find anything, please keep me posted too.