I suggest getting a model that does metered usage instead of timed. Basically you want a unit that runs its conditioning cycle based on the amount of water you use and not one that does it every 7 days no matter what. That way you save money by using less salt and water (for the flush cycle).
Agreed on this point 100%. You can find out from your local water utility how hard your water is. Ours is a whopping 13.3gpg.
I bought a used water softener several years ago and installed it myself. Like OP's, my water main is quite a distance from the utility room, so I had to reroute some of the plumbing, but it wasn't too bad. I spent $80 on the used water softener and about $200 for the rest of the plumbing materials, and did it over a couple of Saturdays. For us, it has been totally worth it. Dishes and clothes are cleaner, showers don't immediately frost over with mineral deposits, soap and shampoo lather and clean way better, and all our fixtures don't crust over or clog.
Other than filling it with salt every once in a while, it has been maintenance-free.
Water softeners are sized based on how much hardness they can remove before regenerating. So a 30,000 grain softener can soften about 2,200 gallons of our 13.3gpg water before it'll regenerate. Getting a "bigger" water softener just means it will regenerate less often, and IMO, it's not worth the extra cost unless you're using so much water that you'd be regenerating every couple days.