I jack up my trailer, spin the wheels and if all sounds good I'm happy. I also have bearing buddies and 2 spare bearing kits in my boat. Better safe than sorry.
Get multi strand tinned copper and proper size battery/wire lugs. Most marine places will have the right stuff or you could order from Stright Mackay. They have everything you need. And when you connect your lugs some heat shrink would be a good idea.