Most toilet problems give you a sign, and it pays to take that sign seriously while the fix is still small. La Mesa households run into the same few problems all the time. If the tank refills on its own in a quiet house, water is escaping past a worn flapper and adding to every bill. If it keeps running after a flush, the fill valve is often worn out. If the toilet rocks a little when you sit, the mounting bolts are often loosening, and the wax seal underneath may fail next. Once that seal gives, the leak reaches the floor, and in older La Mesa homes the floor is worth protecting.
Most toilet problems turn out to be repairs, not replacements. The parts inside a tank can be replaced one at a time, and a solid toilet can stay in service with occasional maintenance. Replacement makes sense when the porcelain is cracked, when repair bills keep stacking up on a worn out toilet, or when you want an upgrade. Modern toilets use less water, and a bidet is worth adding whenever a replacement is happening anyway. Whether to repair or replace comes down to the condition of your toilet.
A toilet that keeps backing up usually has a drain problem rather than a toilet problem, and the drain side has its own service and its own page. Anything that's truly a toilet problem, whether it runs, rocks, leaks or needs replacing, is performed by or under a licensed contractor, explained plainly, and set and sealed properly. You make the decisions, on your own schedule.