Blue screening(?)

What I want to do is to take a video of a kid’s football match and put it over a backdrop of Wembley Stadium (so the kids appear to be playing at Wembley). What software do I need to do this?
Thanks

You'll need a compositing app like Shake and these are NOT cheap! Maybe there are cheaper alternatives out there though.




Edited to add:

Ooh! Seems there is! Final Cut Express has compositing capabilities, according to Apple.

This might help you understand compositing: Compositing Tutorial.

Great, thanks very much!
Looks hard but guess im going to have to learn...

It will take FOREVER. Depends on how long you plan the video to be and how you film it. If you are filming the footballers infront of a blue screen it won't take long because you can just replace the blue with the footage you want. However, if you film them playing on a field then inserting them onto wembley, you will have to cut each person out for EVERY frame (there are 25 frames in a second), each frame might take you 20 - 30 min.

Even longer if he has to do it on a per-field basis instead of a per-frame basis. Also I hope the footage isn't handheld!

Hym, it was on a handheld. Thinking twice about it, maybe kickups against a blank screen will be better next time!

It will be far easier. Make sure the background is one colour, try to get some lights on it to make the colour nice and even. A sheet can work, but if creased it can cause problems. Try and use a blank wall.

I actually bought a green piece of fabric off ebay for green-screening, it works perfectly. I just have to hang it for an hour so the creases drop out.

If you use a solid colour you can just replace it with a background.