Personally, I'd say it's "easy" but with quotation marks. It's definitely not professional work, but there's one thing people often forget to mention: humidity. If your hallway has even a bit of condensation or moisture in the walls, the PVC is gonna shift, it'll come unstuck or it'll get wavy. I've seen that happen with friends who tried it without checking that first. So before you start, really make the effort to check that your walls aren't too damp. If you have any doubt at all, air it out well for a few days, like window open.
For the prep work, yeah it's really the basics. Your wall needs to be clean (dust, dirt), dry, and as smooth as possible. If there are bumps or spots sticking out, it's gonna show through the PVC. Remove the old coverings completely, fill in the holes with joint compound or plaster, sand it. Seems annoying but it's literally 70% of the job. Once that's done, the installation itself? It's really not complicated. You cut it to size, you apply the adhesive (usually it comes with it), you stick it starting from the top toward the bottom, you smooth it with a putty knife or a brush so you don't leave air pockets. Take your time, work on one section at a time, and you're good.
If you don't have too many imperfections on your walls and you can do the prep correctly, honestly you can do it yourself. It's just about being patient and careful during the prep work.