Dual Antenna Question

Hi everyone. I've got a couple of questions that hopefully someone can answer. I'm trying to connect a shed that I have over wireless B. The shed is .9 miles away and I do have line of sight. I'm using a wireless B router with a 10dB directional antenna. Here's my questions.

1. My router has two antennas. Linksys will allow you to disable one antenna and only transmit from one antenna. Unfortunately, I don't have a Linksys. You cannot disable one antenna. Should I connect my directional antenna to just one antenna and leave the other one alone, or will this cause problems?

2. Can I put the antennas into a 2:1 combiner and get more power out of the antenna?

I'm an RF technician, but not a wireless networking wizard so don't be afraid to be technical with me.

Mark