I have mythTV installed and running, everything seems to be working alright. This is what I want to do. I have a pvr-500 card that Im going to use for recording, and a TV-150 card with the IR blaster.

I have that (the 150) attached to my Digital Cable Box, and the 500 connected directly to the wall.

So, I want to set it up to record from the two 500 sources, and watch from the ONE 150. Is this possible, all the while using the grey haup. remote to change and schedule recordings? And in addition to that, can I record a show from the 150 every so often, and watch a source from the 500?

I guess what im really trying to ask is how to change my source while im watching television. whats the key combination?

The key to rotate through your inputs is "y"

If you've got MythWeb working the server includes online documentation. On my box the key binding docs are at: http://black2/mythtv-doc/keys.txt You should substitute the name or IP address of you KM box for "black2".

BTW - You really need to trot over to the MythTV website and read the documentation there. It contains far more than we can reproduce for you.
http://www.mythtv.org/wiki/index.php/User_Manual:Index