opinions on use of sparx with php and xml

[etalinc]

I'm quite unfamiliar with this process, but we're looking for a system for our programmers to work with and this one looks pretty good.  We are hopeful that we will finally have our program documented and be able to go forward better prepared with better planning ability.

May I have some general opinions on the use of this system with php and xml.  
Like general ease of learning...

How long did it take to learn the system to use it effectively?

How many individuals should be involved in generating uml documentation?

We have a program that has already been written so the process is going to be backwards at this point. How does this program assist in reverse engineering existing programming?

Does the system also create white papers along with the development process?

Sorry for so many questions... but thank you in advance.