The little metal door thing falling off is probably causing your evap leak. I don't know if that part is repairable at all, but I'm going to guess it probably isn't.
A new filler neck from Ford will cost a couple hundred dollars. Tituswillfordparts.com is a Ford dealer that sells parts online at a discount. I'd try them if you want new OEM stuff.
If you want to save some money, you will have to go used. I have seen aftermarket filler necks for older Rangers, but not for anything newer than 1994. I had to replace the rotted out one on my 95 Explorer, so I've been through this.
Do you have any warranty left?