I have a 98 750IL with the self-levelling, EDC, electronic shocks. I really don't want to spend $2500+ to change them out and understand you can put in traditional Bilsteins and bypass the EDC.

Has anyone else done this? Any comments?

I think there may be a write-up on e38.org. Some here only change the fronts and have gone with traditional. I haven't done it myself but there is no way in hell I'd pay that much for some struts only.
Good luck.
Also try the "search" function per this has been discussed here plenty.

Welcome to BF.C BTW

So how do I know if the shocks are really shot? The car does have 155K on it. Ride seems fine but I sometimes get a shimmy through the steering around 50mph. I changed the Control Arm bushings to Urethane ones. All front suspension nuts and bolts have been checked and tightened. Front-end has always felt a bit loose over bumps. My '82 380SL Mercedes has much tighter steering/front suspension so somethings up.

Appreciate any advice.