There are few modified Sevilles, fewer modified Eldos, and even fewer modified Devilles. No idea on the appearance mods other than maybe eBay. As far as performance goes the 2 things you can do that are worthwhile are exhaust and nitrous. I think Corsa has a system that'll work with an 00 Deville but check with them; even if they do have a system it'll be cheaper and just as effective to get a local exhaust shop to make you a nice catback with mufflers of your choice. Then stick a 75-100 shot on there and have fun.