for compositing I use adobe after effects. But there are various compositing programs, like "shake" , "combustion" , "inferno" and I am sure there are even more. I can only comment on after effects but in a way it is like a very advanced movie maker. I don't know how familiar you are with adobe software like photoshop for example. But you could imagine after effects like photoshop just for moving image. You work in layers which gives you a great deal of control over the different parts of your movie.
You could for example render your character and it's shaddow or shirt seperately. Now you have two layers. And say you wanted the shirt to change colour or the shaddow to disappear you can do it without influencing your character.
I hope I did not confuse you even more.
And yes you can add sound, I don't know about the other programs but I would not recommend doing that in after effects. I usually use final cut pro or premiere. But for simple sound editing something like Imovie might do it.
Also even though I have never used cloth I am quite sure it is as complicated as all the other parts that come with maya. I am new to maya as well and it is the most complex and complicated piece of software I have ever seen. Propably the most powerful as well. But what I am trying to say is unless you have a personal instructor, it will take up a lot of time to get a character ready for animation. ( I cannot recall how often I yelled at my computer) So if it is not absolutely imperative for your story that the clothes move, don't use cloth but just make a polygon jumper or something else. Also I think cloth simulation might be quite powerhungry.
If you still want to use it I am sure there is a cloth tutorial in the maya help, maybe it tells you at what point to get your characters dressed.