iirc correctly you replace the entire section and not just the armrest portion. the only thing that stays is the ebrake and your shifter. (some one else will probably know for sure, im sure you arent the first to swap armrest.) There will be screws holding everthing in on the front cupholders and then the screw you already found on those rears. then you just unscrew your shift knob. the only tricky part is the e-brake, pull it all the way up and then lift everything over it(tight fit)
I went through armrest withdraw initially going from a car with one to the one with out. After driving with out it for a while and then driving my sisters focus with one, i preferred with out better. That center counsel portion is interchangeable from 00-07, havent heard of anyone with issues with them not fitting (manual to manual, auto to auto of course.) Also, some people with manuals get annoyed with the arm rest, saying it gets in the way of the shifter and ebrake.
Also, your car sounds like a base S model. Manual and no power standard, AC was an option at that level. You will also not have a tachometer or ABS.