First of all welcome to the forums.
No Im afraid that being able to add text to your marks is a feature that did not make it into the final product.
Im taking it you read that in the 'manual'. Since your new here I'll also take it that you dont know that the 'manual' is somewhat of a running joke. It is a kludge of incorrect and erronious features (as you found out) copy & pasted from SH3.
Frankly it serves quite well as a coaster :rotfl:
Fortunatly for you you found the best source of accurate information on the game available. This forum.
Check the sticky threads at the top and there is a wealth of information available to you.
As to the sound your probably talking about the 'mods' that are available. These forums have an entire section dedicated to them. They can do alot more than give you better sound. They can give you a better game experience as well.
Anything you dont find covered there just ask the community is quite helpful and patient... for the most part
This is one place where you wont hear RTFM
