Hi Kerri, welcome!

The first thing I'm going to suggest is that you get yourself a copy of Dr Atkins' New Diet Revolution. All of your questions will be answered there.

Swiching to a low carb eating plan is such a radical departure that trying to do it without arming yourself first with the appropriate information is all but a recipe for failure. So first thing, buy the book, and read it well.

You can eat any sort of lettuce at all - just bear in mind that iceberg lettuce doesn't have as many nutrients as other lettuces such as cos/romaine.

Yes, you can have diet jello.

Diet Coke is not recommended for two reasons. Dr A suggests not to use aspartame (Nutrasweet or Equal) which is used to sweeten Diet Coke. Partly due to the fact that there are question marks about its long term safety, partly because it can slow weight loss for many people. The other reason is caffeine. Dr A strongly prefers we give up caffeine as it can produce an insulin reaction.
Having said all that, some folk do drink Diet Coke and still lose okay.

Reading the book should also be able to reassure you that fat is no longer the "enemy."

Yes, you can eat shrimp.

All the best to you, Kerri.

Rosebud