I have researched this a lot. I was going to do a DIY install, until Sunset Imports dropped the price on their kit to $130.
I was going to use OEM grills, and the brown plug for the speaker, but those parts alone where $110, the kit was just a better deal, even if you replace the speakers.
You could DIY but your going to have problems making the grills, unless your really good at working with metal.
I would just buy the kit because it will be cheaper, easier, and better looking. But if your adamant about DIY, you'll probably just have to figure it out as you go along, and start by removing the storage box. I have not found anything on the internet about a DIY install, except for maybe two people mentioning that they did it.
Good Luck!