If I understand your problem, after removing the wallpaper, you have 'high spots' and 'low spots'. After you remove the paper, as best you can, remove any additional 'loose' paper, and wash the glue residue off. (There are home remidies but I prefer to go to the Home Center or a Wallpaper Retailer and use DIF (by Zinsser).) Do follow the DIF directions to-the-T.
Then, to smooth out the wall, you'll need to apply some Joint Compound. Depending on the severity of your 'problem' will dictate how much you'll need. (Search the WEB on how to use Joint Compound.) This will eventually fill the 'low spots' and you'll be ready for priming.
As a first timer, you need to take your time and forget about 'the least amount of time'. If you want results that way, I suggest you hire a pro for the 'rough work', and then you can do the priming and painting. When it comes to priming and painting, you have to read the paint cans about 'high humidity' rooms vs. other rooms. DON'T skimp, otherwise, you'll be doing the same job over again in 5 years. Use Benjamine Moore, MAB, Finneran & Haley, etc., etc., high-quality paints. They're worth the $26 a can (as is the primer too). Depending, you may need 2 coats of finish paint (one coat of primer). Don't try to strrrrreatch the paint; that's how you end up having to do 2 coats, or 'fixing' the light-and-dark areas.
If you need more info, post up. My best to ya and hope this helps.