Melissa, stripper COULD attack the adhesive of electrical tape, but is unlikely to migrate through the plastic tape, so just be careful around the edges of the tape, and use stripper sparingly, and finish off with scraping. The stripper I use is a gel, so not runny.
It attacks the adhesive of every tape I've tried, but as your obtainability seems limited (as was mine) it is the first option I would try.
The very last bits of the varnish are a bugger to get, but if you don't get them, the new varnish will be patchy.
Don't forget to mask everything you are leaving alone, and do it carefully. A guitar is lightweight, and you will unthinkingly hold it to stop it moving about. Been there, done that, got the fingerprints.
Around the bridge needs careful work too. Expensive guitars have self-coloured wood, but cheap ones, not often. It's unlikely that the glue holding the bridge on will be affected, but why take a chance! another case for sparing use of stripper.
Hope this helps. Chris.