Stereo Amplifier

[flymzz]

Well my first post and wanted to pick some brains on a project.

I am building a portable iPod dock, I found a circuit design on-line and wandering a few things about it, so some help with the following would be great. (I just want to say that i have basic knowledge on electronics but enough to successfully assemble a circuit).

I have attached a schematic of the amplifier circuit and its power supply circuit, and need to know the following;

1: where can I fit in a volume control switch as I can't seem to see it on the circuit.

2: I wish to attach a Sealed lead acid battery to the power supply as the main source, and need to know if any amendments should be made to the circuit to accommodate this.