The heating element for your Greystone F4716W Fireplace in your 2018 Forest River Sierra HT 5th Wheel is not available, unfortunately.
With that being said, since this fireplace & its replacement parts have been discontinued, the best option is a complete fireplace replacement.
I know this may not be an ideal option, however the:
-Furrion RV Electric Fireplace with Crystals - 40" Wide # FF40SC15ABL is a great replacement.
This fireplace is a couple inches shorter overall but the actual... view full answer...
I looked up your Greystone fireplace and it looks to be a 32 inch long model that has crystals which is very similar to the Furrion part # FR88FR which would be a great option for a replacement. We've found that the Furrion fireplaces are more reliable than the Greystone ones. This actually draws less amperage at 12 amps too. view full answer...
The Multi-Fit Motor Home Trailer Hitch, 47" - 71" wide # 82201 is a Class III hitch so you will be good to go with the system your referenced as long as it falls within its capacities. It has the 2 inch receiver opening you need and is rated for 300 lbs tongue weight and 3,500 lbs towing capacity. view full answer...