Replacing speakers, a few general questions

HI, I have an 89 cherokee laredo and would like to replace the 4 stock speakers. Im trying to do this as painlessly as possible by only putting in new speakers that fit into the pre-existing slots, etc. I have a few general questions -

1. When tugging at the door panel i noticed it appears to just be held on by number of white plastic screw-type things. Im scared that once i pull the door panel off these wont go back on properly or not well (i.e. flush with the door like it is now). Is this a legitimate concern? and if so is there anything i can do about it?

2. What are my concerns as far as choosing replacement speakers? That is, do i need to concern myself with wattage or power requirements? Will connecting the new speakers be just a matter of plugging something in or what? The speakers are 5 1/4 that i am replacing, as long as the new ones i buy are 5 1/4 also am i good to go?

3. Anything else relevant you can think of to mention to someone that has never done this before.

4. Oh and I noticed walmart sells like a 2 pack of generic 5 1/4s for like 20 bucks. Will the sound difference between those and a nicer, say, name brand set be signifigant?

They won't go back in if you remove them like a fool. Take your time to carefully pry them out one at a time with a Jam puller or flathead screwdriver. Then to get the panel back on, just push them back in. Don't waste money on cheap speakers. You get what you pay for. If you want low cost quality replacements I recommend Jensen.

Its a really easy job, just take your time to ensure you don't break anything.

Thanks!

Also, its appears (what i can see thru the grills) that the 2 rear speakers are different than the 2 front ones. I think they are the same size (5 1/4), but I think they may have, like, different "stuff" (tweeters?) on them. Is this something i should try and mimic with the replacements i get?

And, is the power required (wattage?) something i need to take into account or do all 5 1/4 speakers use the same amount? I noticed when looking at speakers some said stuff like " 4 - 45 watts" or "2 -25 watts", but im not really sure what this means or if it pertains to my situation.

The power rating of the speakers all depends on the watts per channel rating of your deck or amp.

Ya I started researching it a bit and am kinda getting the gist of it now. That being said, is it possible or likely that the new speakers i buy will be to deep for the slot the current speakers are in? Also being that I will only be using the 4 stock locations do you have any recommendations for what type of speakers to place where? For instance I suppose the best speakers i have should go up front cause they will make the most difference there right?