That's exactly what I ended up doing. Although, the job made me realize how useful a set of 1/4" drive Allen wrenches would be in my toolbox.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles

I believe you can check chain stretch by rotating the engine to 45° BTDC on the #1 cylinder compression stroke. In this position, you should be able to insert the 6mm (?) lock pins into camshaft flanges. If not, turn the engine very slowly until the pins can be inserted, and read how far off the timing indicator is (for example, if the pins will insert at 42° BTDC, the chain may be stretched 3 degrees). The problem is, I believe that worn or damaged chain rails can skew this reading... the chain could be fine, new rails may pull the timing back into spec.

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Is this with the tensioner removed? Does it matter?

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles

No, you check it with the tensioner installed. If the rails are all new, and the pins won't insert at 45°, either the chain is stretched or the cams weren't adjusted properly in the first place. The FSM procedure is at this link.

You'd remove the tensioner if you were to actually adjust the cam timing, per the procedure above (it's step #4). If you attempt this, remember that the twelve Torx stretch bolts for the cam sprockets & two stretch bolts for cam adjusters (14 total) must all be replaced, to the tune of ~$50 or so.

Thanks. The next time I have the valve covers off I'm going to order the pins and check the chain stretch.

__________________
1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles