We installed our own in 1990, with the help and advice of a friend who had worked in that trade. It's a big job, but do-able, if you're handy.
Our original liner is still holding up. We had an expert excavator operator dig the hole, which saved a lot of fine-tuning with shovels. We put a "hard" bottom in, basically 3-4 inches of mortar trowelled in. Probably used an excessive amount of concrete around the outside of the steel sidewalls, but they've never moved. Saved some money on the diy install, but splurged on a wrc deck, which turned out very nice.
Outdoor swimming season here is May-Sept without supplementary heating, but could easily add a month on each end with some solar heat.
It has been our "cottage", since we're somewhat tied to home by a barnful of animals. Never regretted the investment. People who say "pools are a lot of work" usually haven't owned one. There are lots of work-saving accessories.
With our friend's help, the liner went in nicely, but when the time comes to replace it, I'll be calling the pool guys! (The original crew are still around, but we're not as spry now
Good luck.
Peter