I was going to suggest youtube to you. I sat and watched some of the beginners videos the other night and found myself saying "oh, yeah I remember that" quite often. I've just booked a day holiday from work and that's going to be my day for getting to grips with the Knitmaster.
As for how much yarn you'll need - not sure what the proper way of judging is but I do remember that I used to buy cones by weight so my suggestion is that you weigh one of your existing jumpers and use that as a guide to start with. I have some full cones of Shetland and I know that a full jumper for my husband hardly made a dent in one.
How about this?
Craftspun Yarns
The Old Mill, Johnstown, Naas, Co Kildare, 00 353 45 876881
The shop is open by appointment only, but does a good selection of handknitting, crochet and machine-knitting yarns that have been spun and dyed in either Donegal or England for Craftspun Yarns; only a few branded yarns are stocked. It also sells Ashford spinning wheels and looms as well as a selection of knitting accessories.