I'm about to begin changing fluids in my "new" 1981 300D. I have a few questions for those who've done it...

Differential: Where can I find the hex key necessary for this job? Is it a 14mm? I'm considering refilling with synthetic gear lube, any problems with that?

Transmission: any recommendation on off-the-shelve ATF? What standard should the fluid, at least, comply with?

Radiator: The stuff it has now is green...so I think is not the right one. I'm thinking on refilling with Texaco's phosphate-free ethyl-glycol antifreeze (red). That's what I've used in the Audi for over 2 years with no problems. They say it's good for 150.000 miles or 5 years. Even if it's half that, I think it's a good product.

Power steering: any advise on how to flush this system? I will replace the filter as well.

Brakes: I will change the fluid using Pentosin DOT 4.

Engine:I live in South Florida. I'll use Shell's Rotella 15W-40. It's very inexpensive and recommended for diesels. .

Thanks...