Yay! Glad to hear you had a nice drive! What a nice way to start out.
I have to keep this quick but here are a few answers off the top of my head:
Dash Light Intensity - its a rotary switch just above your right knee on the knee padding...cleverly hidden just to make you feel silly when you first buy a S4 Spider.
Gas smell - happens occasionally in the summertime...its been covered in a previous thread recently on AfaBB so just do search
Original Owners Manual....last place I saw them (unfortunately I didn't jump at the chance) was
www.vickauto.com
They have (among plenty of other suppliers too) the original foot pedal pads if you haven't adjusted to your aftermarket ones. They also sell the CD Rom that contains the owners manual, service manuals, etc. Definitely a must have in my book. The company's website has updates for the software so it'll run on Windows XP if you have that....normally only runs on Win 95/98/2000.
Try
www.serpentautosport.com for 16" wheels....
Everyone else will surely jump in on tires & mods....