While this is about shellac on drywall, it can apply to shellac on wood. About a year ago I determined to refinish my bathroom walls.
Removing the wallpaper - Steam does nothing when the wallpaper is vinyl. I got a perforating tool (looks like a computer mouse but with ferocious teeth) It makes small tears in the paper. Spray with water and wait, then peel and scrape. Lot of work.
Removing the wallpaper paste - Spray and scrub 3 or 4 times. Can still feel slippery spots. More work than removing the paper.
Seal the paste residue in place - Gave it a coat of shellac. Didn't want to use my good stuff, used some very old premixed stuff. Stunk like heck, took two days to dry, walls were very streaky with urine yellow gunk.
Drywall repairs - plaster and sand, rinse, repeat till flat.
Paint - with good SW paint, two coats. Replace trim (preprinted) and touch up.
Results - Worried about the shellac and paste. Eight months later it still looks great.