Residential Gas Service

[MissMyBike]

Hi all. Need some advice on residential gas service for our new place at Guanajuato. We just bought a house which has a 300 liter tank on the roof. The tank is dated 1980 & the regulator looks just as old. So obviously the setup has to be replaced. Curious that the hook-up for refilling is right at the tank, meaning the truck hose has to be lifted two tall stories up over the edge of the roof to reach the tank!

I found two providers in GTO: Gas Butano & Noel - Did I miss any? Any difference in the service between the two?
Is it best to buy a replacement tank from the two gas providers above, a ferretería, or likes of Home Depot?
Do the gas vendors install new tanks (including lifting to roof)?
The water heater is electric. Any advantage to switching to gas?
If I switch the water heater to gas, does a 300 liter gas tank seem reasonable or should I upgrade to 500 liter (assuming not too heavy for the roof to support the weight)?

By the way, I read in US & Canada stationary gas tanks have to be installed meters away from the house. This doesn't seem to be the case in Mexico, and I don't see how it could if it were the regulation.

Any advice would be greatly appreciated.