I cant help you out on the modem thing, but the wireless does work with ndiswrapper.
The Dell 1390 is nothing more than a re-branded Broadcom 4311. There seem to be different revisions to the card, therefore slightly different drivers. The best place to get the drivers is the manufacturer of the PC, either the install media or the drivers download page. Also, follow this how-to and you should get wifi werking: http://www.sabayonlinux.org/forum/viewtopic.php?t=2966
PS: Im not sure what you mean by a 16k kernel. I have never used linuxant.com.