PCIe x16 (x4 data lanes)

Hey, guys  . So, I just bought a gtx 260 core 216 o/c. My motherboard is an Asrock 4Core1600Twins-P35. I am going to put my gtx 260 in the PCIe 1.1 x16 lane. The other PCIe slot on this motherboard fits x16 cards, but has x4 data lanes.

I have a few questions:

1. If I wanted to put a 2nd gtx 260 in the x16 lane (x4 data lanes) would it really make a big difference on that kind of card?

2. Do data lanes just provide bandwith? or What do data lanes do?

3. Does PCIe 2.0 double the amount of bandwith for cards that can handle it?

Please reply. Thanks, guys  .