Connect New Antenna Leads In Belkin F7D4302 Router?

I have a Belkin Play N300 (part number = F7D4302) wireless router, and I want to connect my (soon-to-be-pole-mounted) 12DBI omnidirectional antenna to it, the goal is better wireless access in one area of a church camp. I have a couple of U.lf - RP-SMA pigtails on the way, because of course the router doesn't have an external antenna connection.

I opened up the router case, and below is a shot of the board. There's plenty of room inside the case. The router is dual-band (2.4 and 5ghz), and uses 2 internal antennae, apparently it senses the better one and uses it as needed.

My plan is to disconnect one antenna, and connect/solder my external antenna pigtail in its place. I'm a fair hand at soldering, but very little practice de-soldering...

1. Is disconnecting / replacing one antenna the way to go, and if so, which one? Or should I leave them both connected and piggyback my external onto one of them (soldering the leads on top of existing connections), or disconnect both antennae, or does it matter?

2. Which set of wires, white or black, are used for which band - and should I connect to? I assume I'd want to hook up to the 2.4ghz, correct?

The white wires come out from the tiny Broadcom chip, I think it's marked BCM43224KMLG (dang, that's some tiny print!). This page leads me to think that these are the 5ghz antenna leads, but I'd llike to be positive before I start cutting.

The black wires appear to feed from the larger Broadcom chip marked BCM4718A1KFBG. Again, this page leads me to think that this is the 2.4ghz antenna.

3. Assuming that the black wires are the ones I want, would it be ok to cut one really close to the board end, cut the U.fl connector off of my pigtail, prep the wire / shielding, and solder the wire / shielding on top of the existing solder connection?