Yeah you are gonna probably want to get an amp for the components or any aftermarket speaker if she likes it loud.

As far as installing goes- the 2-way or 3-way coaxial speakers (means tweeter sitting with woofer on same axis) are pretty much plug and play depending on what depth they are.
For components (woofer in stock location, separate tweeter) installing the woofer will be relatively easy but finding a place for the tweeter might be a little difficult.

My first install were infinity 605cs components and it took me two days to do it. Mainly because i had to go out and get alot of parts like wire, door panel remover, etc...

have fun...