Well the big sticker things are called overlays. You'd have to sand the entire playfield top down and then apply it.
The other way is to paint/touch up the PF and then clear coat it.
Either way, this is a big damn job. But here's an overload of info to get you started
https://pinside.com/pinball/forum/topic/vids-guide-to-ultimate-playfield-restoration
EDIT: For a total bang up job, a brand "new" playfield is the best bet...but very expensive and possibly hard to find.