OK - I jacked up the back of the car, put it on jack stands and crawled underneath. Interesting - this fuel tank has no strainer! Just two hoses, clamped to nipples. Sprayed the clamps liberally with PB Blaster, and let it go to work - not that it turned out to be all that necessary, most of the clamps were so rusted they just about fell off when I applied any torque to the clamp screw. Amazing that the rubber lines did not leak.
The 3/4 gallon of fuel (dyed red?) came out - not very much water in there at all! While that was going on, I removed the right rear wheel to take a look at the brake pads - I have to consult the manual to see how thin is OK. There's a bit of ridge around the disk, so I suppose they will have to be replaced when I change out the pads...
Once the tank emptied, I installed some nice fresh Gates fuel hose and new clamps all around. Hopefully, I won't have to think about them for a while...
Here's a link to my photo album on the project:
http://www.spottydog.us/Photos/benz/index.html
Next is to take a look at the brakes and replace the master cylinder. The old one works fine, but is leaking around the reservoir seals and is a rusty mess... Lucky the car came with a new one in a box.