RCA Problem With head unit. Please help

was not sure if this was the right section to post in.

But I really need some help here. I have a kenwood DDX6019 head unit. I was recently hooking a new amp up in my car when I accidentally touched my rca's with a hot wire. My sub RCA output no longer works. My fronts and rears work fine still. I checked everything. Sub is ok, amp is ok. It is just the SUB RCA output from the unit that is bad. I took it apart to look inside and all the RCA's (sub,rear,front) all come down to one plug and plug into a circuit board inside.

Here are my questions.
#1 When a RCA fries on the head unit is it actually something just inside the head unit rca? or maybe is it just the end of it?

#2 Would it possibly fix anything if I wired a new end on to it?

#3 Instead of sending it in to get it repaired and spending about $120 should I just try to buy a new set of rca's and plug them inside the headunit?

any other ideas or suggestions would be greatly appreciated. Thank you