Service Engine Soon light on 99 SL2

Just bought this car, has 66,200 on it. Service Engine Soon light is coming on. The engine seems to be running fine, except the idle may be high - it's a 5-speed, idling at 1100 rpm. What should I check first? What's the best after-market manual?

Pat

personially i like the haynes repair manual, but chiltons works fine.

go to your local auto part store, many read codes for free.