A habernaro pepper is
VERY hot and looks like this:
http://www.foodsubs.com/Photos/chilepepper-habanero.jpg
You can usually find it in regular supermarkets and if a produce person says they have never heard of it ... well, that's sort of scary.
But, unless you like things HOT HOT HOT, just use a jalepeno.
The jerk seasoning is just my own personal thing, as it usually is something I have in the fridge.
You might want to try a basic recipe first and then add cumin, jerk, etc.
I forgot to say that I put garlic in mine -- that IS very basic.
There are usually two schools of thought on mayo in guac. It's not used in so-called "authentic" recipes but very often sour cream or mayo is added to guacamole in the US. Many people prefer it that way (esp. with sour cream) because it makes for a creamier dip. Usually if you want it creamier you also mash the avacados to a smoother consistency.
I personally don't care for mayo or sour cream IN the guac and like my guac sort of lumpy.
DONT FEEL LOST!!!
I would suggest trying the variations that are suggested here --
as well as your own ideas -- to see what you really like.
You could start by making a bowl of basic guac and then separating it into several differetn bowls and then adding things like mayo, sour cream, cumin, jerk, hot sauce, worcestershire sauce, etc, and doing a fun little taste test! A few Coronas or Tecates wouldn't hurt either!