DDJ800 - RIght RCA Channel on Master Out is Dead - Repair, or Start Using XLR Out?

The right channel on my RCA master out is dead - using RCA cables, I'm only getting sound out of the left channel. I'm thinking that the easiest thing to do would be to buy some XLR to RCA cables and start using the XLR out, but am wondering if the right channel will be dead on the XLR out also, or is that a separate unit? If I can use the XLR outs, since there are left and right channels, I'm assuming I need to buy 2 XLR to RCA cables, but I read somewhere that for DJ controllers, the sound coming out needs to be mono in order for the bass to come through. That obviously isn't the case with the RCA outs, but just wanted to make sure I buy the right XLR cables - are there any requirements for the XLR cables? I'd like to buy longer cables (20 feet or even 50 feet), but am concerned about latency / delay with longer cables - will there be a noticeable delay / latency with 20 foot cables or even 50 foot cables, or will I notice a difference between 20 foot and 50 foot cables?

If the XLR out will also likely be dead, where can I get the unit repaired? Is it reasonable to get it repaired in the next 4 weeks, as I have my first gig in 4 weeks and need to bring my own gear for it. Thanks.