For a bike rack you need the hitch only.
For a trailer you need all that. Like magicbus said, I'd skip the ball mount and ball for now. You can grab those locally at several places.
It seems almost every thread about tires here is in regards to the 17-inch rims.
I saw one thread with an 18-inch wheels and the Falken Wildpeak A/T 245/60 R18 was the recommendation. I know options are more limited at 18", but is that pretty much the only option? Is that the biggest tire that...