Well for the fronts u have 3 options really - Replace with a good set of 4" speakers, go for a set of 4" splits (u can get ones with Crossovers but they'll cost u more) or make up a set of pods and put in some bigger splits. ATM i have sony 4" but im gonna make up some X/O 4" out of blaupunkt stuf when i get some money. To put these in its basically 6 screws and of course wiring. Puttin the HU in might be annoying as youll more than likely have to use original mouonts and cut out the double din area. Thats what i did on mine.
GL