my stock sub is blown in my 05 TL

i want to instal aftermarket subs and an amp, is there anything i should know before doing this? ive installed subs in older cars but i dont want to mess up the bluetooth phone thing or anything else..

also if i could use the stock headunit to control the subwoofer that would be awesome!

and were is the best place to wire the LCA so i can keep the stock headunit?