Replacing front speakers with 6.5's, have questions

[youngmanvr4]

I'm in Houston, Tx right now and my car is in Cali. I'm flying back there on the 11th to pick it up, then I'm driving to here (tx) on the 13th and the trip out I found out that my head unit rocks but matched with stock speakers it makes everything sound so bad. So before I make the trip back I want to replace all 4 speakers. But I'll only have 2 days to pick up the speakers and install them. I wont even be in Cali for 48 hours before I leave for the trip back. So with that little time I want to make sure I got everything down.

My plans are to do the 4x6 to 6.5 conversion in the front.
But my questions with that are

1. Do I need to rewire anything to make that conversion? It should be as simple as just taking off the wires on the stock's and hooking them up with the 6.5's right? Anything else?

2. I know I should by-pass the stock amps but I'll have to use head amp power for now. I also dont totally understand how to do it so please walk me through that one. What wire(s) do I tap into for my head power?

For the rear I'm planning on just getting some nice 4x6's for them for now.

Again, I wont have time for mess up's or tying to figure things out. I need to know most everything before I go back there on the 11th. I've done some searching, but some of my questions I couldn't find. Thanks for your help, Nate