Dont do a cold air intake if your planning on driving the car a lot, problems with sucking water into the intake. If you want a intake for your SL just but the cheap Ebay intake, then buy a better filter (like a K&N of Matrix) the one they give with the kit is kinda iffey. A intake is WAY to easy to install to even think about paying someone to do it. I do recomend to buy this...
Intake Support Bracket*-*Mitsubishi 3000GT*/*Dodge Stealth. It holds the intake in the right spot so its noy laying on the thermostat housing. Like the last guy said Downpipe and Test pipe is the biggest upgrade you can do for a SL, you should see about a 20 HP increase and you will red line a lot faster.