You're better keeping the warranty money in your bank and save it up to pay for things yourself. The terms of these warranties are so poor, they are weighted in favour of the insurance company giving the warranty (even optional BMW warranty is insurance backed, just like 'warranties-r-us').
Chances are you'll come out on top, its just a gamble, but the odds must be in your favour otherwise the insurance co wouldn't make any profit.
But if you're planning on keeping warranty, you really need a decent code reader like a Bavarian Technic cable.
Unless you can be sure you've reset / deleted any codes before taking it in, you could leave yourself wide open to void warranty.
The JB4 will delete codes, but only when it's connected, you might activate some codes when removing the unit, and then you're stuck as you can't check if there are any codes.
E63 AMG here at last!