1996 ram 2500 4x4 cummins, best place for parts? front pinion seal?

[rockwind1]

i just got this truck, it was my uncles, he passed recently, he bought it new in 96. put 260k on it but it runs great. i need some parts for it, like right now i am looking for a new positive battery cable, the one that goes to the starter and 2 other things,, it is 3 cables coming off of it, one really big,, medium, and then small. can't seem to locate the right one.

also, it looks like the pinion seal is leaking on the front diff, at least that is what i call it. i've heard its a ***** to replace,, true?

also,, best place to source a front grill,, 3 of the cheap plastic tabs are broken off mine.

thanks for any help, cross posted