How do you replace bumper light bulb 1998 Mercedes Benz E320?

Are you talking about the side marker bulbs on the front bumper? These bulbs should have a access panel from behind them. Look in front of the tire, on the front part of the platic wheel well liner. Should be a small hole that has a release tab, press that tab to release the side marker lens. Then you can just pull the old bulb out, and re-install.