Bigedmond,
Just search YouTube you'll find tons of videos showing how to re pack your bearings by hand. It's messy but very important routine maintenance. Just be sure to get good quality high temp wheel bearing grease and a new seal for each of your hubs. (you'll see they're on the back) they are cheap. I go to trailer tech for my parts.
As far as tires go, I'm in the same boat. 32ft weekend warrior I bought used 6 months ago came with cheap tires. Repacked all my bearings and properly inflated before halloween trip to Dumont and blew one on the way back. Luckily I have 16 inch rims already so I'm going with 235 85 r16 BFG Commercial LT tire. Looking forward to peace of mind.