HELP NEEDED!! batching, overlaying, background cut out

Hi All,

very new to this.

I have 2500+ images (caracitures of cars on white backgrounds). I need to place ALL of them on to  a BLACK tee shirt image for internet listing.

So, how do I do this automated?

make the thing background BLACK

overlay image on the teeshirt

save it in the order they are done

2500+ times

I use Photoshop 7.0