Rebuilding my sl r129

hello, i will buy me an r129(sl) but the 5400. i'm from belgium an I had some friends who did the same. What they did? Thay rebuilt there old sl to a new one. Only at the outside, but do you think it is good? And does anyone knows where in europe I can tune my car? you can see pictures of changed cars at www.vhline.be and select sports line. What do you think about it?
Does anyone know a navigation system for my sl? Because I want a big screen, but fitted in the dashboard, not such one that they built on my dashboard, but a screen that fit in my dashboard. I now that you must change a little bit to your dashboard if you want to, but please help me.