I'd recommend a Fiberfloor. I like the Tarkett brand. Link to what I used in my van: http://www.classbforum.com/phpBB2/vi...t=fiber#p12301
Fiberfloor easy to work with - I cut it with scissors for complicated pieces and a utility knife for longer straight runs. It doesn't curl up at the edges and there is no cardboard or paper in it.
Engineered fiberglass inner layer - - - Utilizes woven fibers so it lays flat and won’t expand or contract for increased stability
You can get a piece at low cost at an "end-of-the-roll" flooring outlet.
Re: Water Heater - it is not that difficult to replace - time consuming because it is sometimes very hard to access it depend on where it is located. You have to understand the 12 volt and propane connections and safety etc.. These tanks haven't changed much over the years so you should be able to get an almost exact replacement. Here's a link with a bit of info when I installed a new one: http://www.classbforum.com/phpBB2/vi...&t=1880&p=8974
The water heater will come with very good instructions. I replaced mine with a new one having the same specs and features so that makes the job easier. Mine only runs on propane and it is a DSI (Direct Spark Ignition) model so I can turn it on and off from inside the RV via a switch. It is not a pilot light type model. At first I was going to install a model with an electric heating element in addition to propane but that order got messed up.
Yours will probably be either an Atwood or a Suburban. I was able to use the original outside door with my new water heater.
Re: batteries - two batteries are better. There will be less stress on the batteries because they most likely won't be discharged as deeply.
Ideally batteries grouped together should be the same age and capacity.