I know this might be a bit...late...but I have 2 good resources.
Dan Potter, over @ CA Games did his own DC LED mod a while ago. You might want to check out his allusion.net page for another opinion on the project.
For the Dreamcast cases, there's a local import store in my area that used to carry them. I'll be going there this comming week. If anyone is still interested in clear (colored) DC cases, I'll post an update to let everyone know if they have any left and what the price is.