Replacing Speakers

[T Sport 1978]

Hi all,

I am looking to change the Speakers in my 5 door T Sport.

I am a total imbecile with this kinda thing, and i really need help from the ground up!

First of all, how do i get to the speak enclosure and can anyone give me the correct size of the Speakers that i need to purchase?

I have read that it is 6.5" for fronts and 4" for the back...is this correct? I cant find this information anywhere.

Secondly, can i just use the existing wiring to connect to my to-be-new-speakers?

Any input is much appreciated.

[g3m xr]

sorry i havent a clue lol