Not difficult to hang wallpaper but depends a bit on your walls and your paper. If walls not straight or difficult pattern to match up can be a nightmare. Get organised first - pop off to Homebase or hte like and get paste, paper brush and a little roller for the seams and a good sharp pair of scissors and a blade for cutting.
re: paint - depends what you're painting over . Wallaper or strong colour or plain white walls? Also what you are using - a roller will probably mean at least 2 coats in my experience.
I was thinking about a roller but not necessarily. We're stripping all the wallpaper off so it'll either be lining paper (if the walls are bad) or plaster (if they're good or were so bad they needed doing). I know this sounds vague but until we pull the wallpaper off we don't know what we're facing.
Good advice regarding getting the wallpapering stuff ready. I know my Mum said when she first tried to do it she cried (and she's generally quite a determined lady!) but I saw 6 rolls of lovely wallpaper yesterday that were £1 a roll from £17!
If you paint over fresh plaster you need to use watered down emulsion first then a second coat of less-watered down emulsion then a final coat of undiluted emulsion. Not necessary if it only a skim of plaster I believe but certainly if it normally plastered.
I find on coat of 50/50 water to pva is fine for a sealant coat on new plaster...it's what I always do and no paint probs as yet. Regarding the wallpaper...er...I'm pretty good at all things DIY, never again will I paper...I'd rather skim it!