That should be really easy. I use a stripper like Strip-Eze (I think that is the spelling). You apply the gel type liquid, the finish bubbles up, and you scrape it off with a plastic scraper. Use toothpicks for any crevices that the gunk builds up in. After you have scraped it off, there is a residue & I use a wet cloth (not sopping, just wet) to scrub that off. Then go over with a dry towel. After the piece is completely dry, like 24 hours later, sand to a smooth finish.

Then you are ready to stain & seal. I would go to an unfinished furniture shop & get their products, as they have worked better for me than anything I've found at paint or Big Box stores.

Be sure of your wood before doing this. Make sure it is solid wood and no components in it. If not, you could create a mess.

If your denim-blue finish is paint, a stripper will do the trick. If it is a stain, you may not be able to get enough of it off for a maple finish.

Also, (since you don't know what kind of wood it is ), a stain may go on blotchy.