Liner can be DIY'd, if you have one or two helpers to help you stretch it in as the pool fills. You generally want to fill the pool up to just below your stairs while walking and stretching the liner into the floor and corners, then cut in stairs, lights, return, and skimmer, and then finish filling. Usually a 2-day process.
But cost is high and probabiliy of a mistake when cutting in stairs and even smaller fixtures is huge, so I'd just hire a local installer to do the job. It'll cost more than DIY, but less than screwing it up.