Ken,
I took a look at your reservoir at the shop the other day. I think your issues are:
1. The floats inside the reservoir that make contact when the fluid is low and provide the low fluid signal/light--these need to be replaced and are sold separately;
2. The black rubber insert that keeps the fluid from splashing needs to be replaced.
I think your reservoir looks fine and will clean up nicely. I don't think you need to replace the reservoir, just the floats and the insert.
Best,
Tom
1971 280sl Tunis Beige Metallic (restored & enhanced)
1971 280sl Tobacco Brown (low mileage stock)
1970 280sl Deep Red (Project Car)