If I have two CPU's on the board, can i run 2 different aptitude processes?

For example installing apache on one and php on another simultaneously?

Probably not - lock file will prevent it.

No.

It may be possible to set up some amount cpu allocation to help assign some part of the work to each processor. I forget that command. Not sure it would help you at all. Almost every distro is SMP aware and most modern programs are SMP aware. Linux has a scheduler to assign tasks between the processors as needed. You can sometimes assign more cpu power to one process or the other.

Pretty sure that is correct.