I'm not a pro, but I've done what you propose to a 500E. Do I qualify??
Before you pressurize the system, simply replace the brake lines....I strongly suggest you allow penetrant to work on the conections for a day or so. It was utterly simple. Then bleed the brakes as directed by the manufacturer of the bleeder you buy, which essentially involves pressurizing the system and bleeding the furthest wheel from the master cylinder first (RR,LR,RF,LF). I like to swap between blue and yellow fluid-makes it readily apparent when the old stuff is gone