You may want to check to see if the bolts are intact as well as the bowl itself.
The sewer gasses are coming back up from a vapor leak somewhere in the waste line. In my experience as an amateur DIY'er it is most likely that the wax ring directly beneath the commode unit has failed and is allowing the gasses to come back up. I replaced the wax seal yesterday and it made no difference. I even crawled under my home and examined the plumbing underneath and everything was dry and completely odorless. It really has me stumped, the only thing that i haven't tried is replacing the commode. It is about 20 years old but appears to be in excellent shape.
One reason that a shower would leak even after replacing the Delta cartridge could be because of the O rings. You may have to replace them.
Non, replacing a water pump will not cause a hose to leak.
If a coolant leak were caused by brake work, I'd never have that person work on my brakes - ever. Just the brakes, I would think it highly unlikely that it would result in a coolant leak. If they were replacing the master cylinder, then I could see a possibility of someone inadvertently causing a coolant leak, but that would still even be a stretch.
If they leak, they need replacing. No, if they leak they don't need replacing. If they have been scored or eaten they need replacing. If they only leak they need to be re-packed.
It would depend greatly on where the leak is coming from. Need more info.
Sounds like you have a water leak somewhere. It could be from a roof leak, or maybe an upstairs commode, or maybe a water pipe, in your wall, broke.
Do A compression test and a leakdown test too, This will tell you if you have A internal leak. The compression and leak numbers are not nearly as critical as the numbers being within 20% of each other across all cylinders.
Remove the commode and flooring. Dry it with a dehumidifier for a week and evaluate the damage.
Check to see where the leak is coming from. Often it is condensation from the bottom of the water tank and a tray can be purchased to catch this. If the commode is leaking from the base, you probably need to replace the wax seal and that can be a big job for a novice. Also check the water feed line from the floor to the bottom of the tank and tighten if needed. Replacing washers or just tightening connections may be the solution.
bad check valve or a leak.
you should find out where the leak is, contact the customer to tell them what you have found and what you need to do.