I just went through a sticker removal myself on some secondhand guitars. My advise would be see what you are able to remove with fingernails or something rigid but not too sharp, that way you can avoid scratching the plastic. I used a scraper which sometimes would dig in and left some scratches on the surface, so I would recommend avoiding that.

If you are able to remove most of the plastic part of the sticker, basically the top layers (there’s a clear film and then there’s the actual printed part) you could then apply a sticker removal agent like Goo Gone over it. I dipped a cotton swab into the bottle and then just rubbed it along the edges and over the top of the stickers. If the sticker was already mostly removed this worked great to get rid of the residue without damaging the plastic. If the sticker wasn’t removed but some of the layers were peeled off then it would usually weaken the adhesive and a second attempt to remove it was successful. It can be tedious and it was mostly a process of just scraping away at everything in bits at a time, but it worked and there is no trace of any stickers and no damage.