Much good advice above.
NEVER use silicone on the outside of a RV. It is extremely hard to remove thoroughly enough that you can re-caulk over it. A brand called Dicor is a good type to use on the outside. It comes in a self-levelling for horizontal surfaces, and non-levelling for vertical applications.
Definitely sanitize the water system; there are lots of tips on here on how to do it. Use 1/4 cup for every 15 gallons of water in the fresh tank, and open all lines until you smell the bleach coming out. Be sure to include the outdoor shower if you have one. Let it stand 12-24 hours. Then drain the fresh tank, fill with clean water, and flush all the lines. Do this a couple of times and the chlorine taste will be gone.
You need tires.
Go over all the seams and roof penetrations with Dicor.