A licensed electrician will definitely know what to do. If the conductors are large enough, they may be able to simply resize the breaker and install a 50A receptacle. Most likely, though, they will have been sized for 30A so you'll need to pull new conductors. Was it in conduit all the way from the panel to the pedestal?
Do make sure your electrician knows which type of 50A receptacle to install. You might point him or her to an online photo (like eBay) of rv-specific pedestals if you want one.
There are two styles of 50A receptacles, but the one commonly used on RV's is also more common in commercial electrical work as well. The other one lacks the "neutral" leg for 110V and is common only on welders and single pieces of equipment.