Replacing speakers for me punto

[jibidy]

Punto MK2 03 facelift version.

Im looking to replace my front door speakers. I'm looking for at least 40W RMS

What size/depth limitations do I have?
How much of a job is it...how much of the door do I have to remove?

Anyone got any good recommendations?

I dont really wanna spend more than £60

Thanks guys.