Readers digest do a good DIY book, everything is covered from wallpapering to fixing guttering.
Also if lining buy a heavyweight paper, they do one with a slightly rough (like parchment) finish that is good for covering rough walls. It's also easier to hang.
With the gloss don't strip anything unless you have too, you'll be making more hard work for yourself. Basically you need to key over all the old gloss that’s good and feather edges where it’s chipped down to wood. Also don't forget to undercoat bare wood. Consider using something like an egg shell paint on the gloss areas (unless you really want a shiny finish) it's much easier to get a nice finish & IMHO looks better. Getting perfect shiny gloss takes alot of prep and skill.
Don't use cheap sandpaper/sanding discs its false economy and will take you much longer as the paper degrades much faster.
For materials see if you have something like a dulux decorators centre local or a good builders merchants with a decorators section. They can give good advise on paints/brushes etc and it should be cheaper than focus/B&Q. If you find one of these places don’t feel afraid to ask questions no how matter how stupid you think they sound.
Mick just noticed you are in Yorkshire, if not too far from Skipton I'd be happy to give you advise on the jobs. I'm not an expert but have renovated a couple of houses and done more decorating than I care to remember.
