E70 Battery Replacement - DIY

[Zoich]

1. My OE battery that came with the car says its sealed - I assume it's AGM. The white sticker covered all the traditional caps on the top. YET on the side of the positive half, it is attached to a vent hose and tubing venting out through the bottom of the car? I shook the battery a bit, no slushing liquid sound like when I shake a wet battery. I suppose they install they attached the tubing in case you buy a non-AGM battery? (Without reading the forum, I did purchase a wet one from Batteries Plus for 139.00, I am returning that now) I didn't realize how complicated and that I needed to consult this forum until I couldn't find the battery. Different than my previous e39. The batteries plus one wet one slushes, and the top caps are not sticker sealed. Their AGM had to be special ordered and it was 189. So am I right that ours is an AGM battery?
2. What if I don't register? I still don't get it about registering... Register meaning to tell my car there is a brand new battery? So charge at a different rate as oppose to an older battery? I would go buy that tool32 and some kind of OBD tool - but really? It was 200 bucks after 5 years plus with the original one, should I really care? Am I looking at potentially costing more than 200 dollars for another battery replacement or you think my car will have some expensive electronic issues if I don't register the darn thing?? Thanks guys.

When did cars get so complicated?