There is nothing to "renew" with solar modules. The solar cells are encapsulated so either work properly or don't. You can test them by measuring (with your clamp on multimeter set on dc amps)  how much current the module supplies to the battery on a perfectly clear day when they are pointed directly at the sun. To be sure they're pointed at the sun you can place a stick or bar perpendicular to the surface and it should cast no shadow. Look up the spec for max power current (aka the Imp) of the module, you should be getting pretty close to that number. 

That link does not appear to include a battery charge controiler so you will still need that.

 The other thing you can do is check your local craigslist for left over residential (about 250 watts) or industrial (about 350 watts) modules. You can often get those for 50 cents a watt or so.  You will need an MPPT type charge controller for them because they run at too high a voltage to charge 12V batteries directly. 

I am just scared of cutting into the wall!!!!

Just in case,

A basic system is Panel(s) --> Charge Controller --> Battery (ies).  The charge controller must be rated for a higher voltage than the highest voltage on the panel(s) and whether you've connected them in series or parallel. 

May I recommend you run the panels at a higher voltage than the batteries and use an MPPT controller.  That will get you a few more minutes of charge time at the ends of the day and/or when the sky is cloudy. 

The electrical connections are pretty straightforward. You will need a multimeter to confirm what you are looking at, so buy one if you don't already have one. You will find it useful around the trailer for many things. Try to get one that has a clamp on feature that can measure dc (not just ac) currents.  All of them should be able to measure dc and ac voltages and resistance (ohms). Some also measure capacitance which could be useful in the future. 

Any advice or direction would be helpful. Go Power does not have any instructions and today I chatted with someone who just said, "Connect this and that and cut a hole and wellah!" Uh huh.