Will my screen work with sound system?
If you do it yourself and know what you're doing, your own will be better and easier. But yes, the electronics package can be made to work with whatever you want to do except amp up your speakers (well maybe you could, with alot of line-out convertors? I'd have to look into it), and if you add a subwoofer you will have to adjust the gains/bassboost through the amp since the stock nav screen won't have any of those options.
Don't buy any factory equipment that you plan on upgrading, IMO.