Thanks samiam4 and good luck! I bought a rebuilt one for $155 from www.benz-store.com and it'll be here in a few days. Only $25 core and I'm tempted to keep the old one--I've heard it can be a simple soldering job and it might be worth experimenting on.

If you have any further tips on making the exchange I'm all ears! I see that the instructions from GDL start after removing the kick panel, and a quick look suggests I don't even know how to do that!!