You made the right decision to hire an electrician. You can run your 50 amp camper from a 30 amp outlet, but you are limited to only 30 amp usage for the entire trailer. Power management is essential when plugged into 30 amp.
I installed 2 different 30 amp RV outlets for my previous camper. Yes, 2 location at the house. Then later, I had one swapped out for a 50 amp outlet. I also hired an electrician and I purchased the RV electric box separate from them.
I ended up getting a 20 - 30 - 50 amp box, so I can still plug in a 30 amp trailer at that spot again, if I ever want to or need to. The entire thing is then wired into an 80 amp breaker in the main box. And #6 wire was used.
The electrician supplied the wire and did the install. It cost me about $250 for their labor and wire, and it cost me about $100 for the RV box.