If my draw length is 29" andI put on a dloop will that change everything? Will I be slapping my wrist while releasing?

You might need to adjust the bow's draw length down a half inch or so, or adjust the length of your release, to compensate for the length of the loop, but it won't make any drastic changes. Shouldn't cause you to slap your wrist at all.

A loop doesn't change a persons proper draw length what so ever. Yourarms don't shrink just because you put a loop on your string.

What it does change is where you anchor. You will need to make up for the aditional length of the loop by making the release shorter.

The D loop hasn't changed my draw or anchor but then, I'm shooting a thumb trigger release not a wrist strap. You could just keep it as short as possible (see Greg's post about tying in a D loop) and twist the string up 8-10 times to dial it in where it needs to be.

Another option, if you like a wrist strap, is to use a release where the trigger is very close to the attachment point of the string. Like the Short 'N Sweet release. Don't do the D loop and wind up with an anchor point way back under your ear.