that amp would over power the sub a little bit but you would be fine, you shouldnt ever be in any trouble...
as far as chanels.. the easiest way to say this is just plain "no" with only 2 channels and all stock stuff amping any other speakers is gonna blow stuff up..

as far as installation... well i'll start by saying i highly recomend a new headunit while doing this because the factory headunit doesnt have subwoofer controlls nor does it have the required RCA outs to send the information.. BUT if you search enough youll be able to find an RCA converter out there for this type of job (still dont recommend it, its kinda a pain in the ass) but once the headunit situations good you have to buy a Amp wiring kit (Here and then it all comes down to plugging and running wires.. its not a hard ordeal, BUT if its your first time you will be confused a bit and prolly will take 1-4 hours depending on how clean you want it to look