Xmas lights are easy. Get a black 90° flat plug extension cord and plug it into the 110 outlet on the back of the console. Run it under the passenger...
The trick with mud tires is to have them siped at a tire shop for winter use. I run cooper STTs (37x12.5)on my JL and have done so for the past year....
Can't speak directly about the Uniden 520 as I have not installed one but I am running a really compact Icon race radio on my JT and it bolted right...