Shortcut
I suggest just using one of those basic level (4 dip switch) garage door openers that you can find at the dollar store. Just pop it open, tie button closed, replace the switchs with transistors(See note), and attach wires from your CPU.
One question that I should ask, is whether or not you already have the receivers on your lights(or atleast built). If so, you will have to take off the resistors and replace with trim pots. If it has an IC, just take it off and wire past it.
If you don't have any receivers yet, it is even easier, cuz' then you can just correspond with the built on resistors.
Notes:
Just to protect both your CPU and circuit, I suggest using opto-couplers(MCT2E) instead of regular transistors(Also makes things easier).
In the end it should look like my pic.