De-winterizing can easily be carried out at home but I'm going to suggest that you take it to a dealer. Get them to check the anode rod in the water heater. It is a piece of sacrificial metal that is meant to prevent the Suburban brand water heater itself from rusting. The anode rod should have be checked when the RV was winterized but it is better to make sure. If you want to check that yourself you'll need a 1 1/16" socket to fit the head of the anode rod on a Suburban water heater. And you might need something like a breaker bar to give needed leverage because it can be very hard to get off.
Do you know if your RT was winterized by using compressed air to blow out the water lines or if RV antifreeze was pumped through the plumbing system?
RV antifreeze is not toxic and can be drained out as if it was just water.
If you still want to do it yourself then here's a well written tutorial: http://roadtrek190popular.blogspot.ca/2 ... fresh.html
You would need to add the step of draining the RV anti-freeze from your fresh water tank first located near the driver side door but under the van after first switching the interior tank valves to summer mode. The author of the tutorial did not add RV antifreeze to the fresh water tanks because he had an aftermarket winterize kit installed that allows RV antifreeze to be directly drawn into the plumbing thus bypassing putting RV antifreeze into the two fresh water tanks when winterizing the RV.
It is much easier than it sounds