Generally, the front sway bar will only be under load if the suspension struts/springs are compressed asymmetrically. If your ramps and rear wheels are all on a level surface, there should no (or very little) load. To make yourself feel better, undo the two center frame mounts first, then disconnect the control arm connections. With the two center mounts undone, it's almost impossible to load the bar.

J. M. van Swaay

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1994 E320 Wagon, 230,000 miles
1995 E320 Sedan, 106,000 miles
1994 E500 Sedan, 79,000 miles