Hi,
I have done this on our 1984 E30+ and it worked well. I am assuming you have teak and holly veneer plywood. The key is to not sand it too hard or deep, as the veneer is quite thin and once you sand through it, it's ruined. I used 120 grit carefully by hand on a small hand pad, then 180, then 220. Vacuum carefully to get rid of all dust.
I used semi-gloss varnish--gloss was too shiny/garrish looking, and satin was too dull for my taste; the semi-gloss looks really nice in my opinion. I applied three coats, with light sanding with 220 grit between coats. The hardest part was ensuring I didn't slightly miss any spots and finding the hairs that fell from my head and my beard as I was varnishing--I managed to pick them out, but I also learned not to go back over any spots, as that remains noticeable once it dries. It's better to sand lightly again and apply another coat if it doesn't turn out well.
I am no expert at this stuff, so the pros might have better advice for you.
Good luck!
Frank