8 speaker system upgrade

My '04 has the 8 speaker setup and one of the front door speakers are shot. Previous owner replaced the head unit with cheap aftermarket, but im not a fan and will likely replace again.

Ive upgraded speakers in every vehicle ive owned, but this one is a bit more in depth then im used to. Seems most of these (all?) are one way/component style with high or low pass filters. Never dealt with those.

Im not looking for high end/audiophile quality...just fuller sound. Perusing Crutchfield, I see most of the sizes listed so that helps.

Ok, so my questions...

Would it be best to stick with component style? If so, using the factory wiring (hopefully), would I need to purchace seperate filters for each speaker? Are they all one way?

The factory amp...can/should I reuse it for the new speakers? Any idea what kind of power it puts out?

Are the Crutchfield specs correct? Anyone know what tweeter size fits well in the door (they dont have a size for that)? I dont mind modifying the openings a bit to fit something larger...if its better. That said, i hope to button it all back up with the factory grilles.

And can anyone school me on the actual wiring (These in series, parallel? How many channels are there? What ohms should I be looking for?).

Thanks in advance!