Tutorialized- Has a great variety of tutorials.
Anyway, follow the advice of the older members. I tried to do what you are doing, and failed. It put me of AS'ing for ages.
No offense but if you don't know how to access and play another movie clip, which is really the most basic piece of script that you are going to come across, I really doubt that you have made a couple of side scrollers. Sure you may of "made" them by copypaste, but not by actually piecing code together.
Break everything down into little bite sized chunks. I.e. work on arrays/variable, then may be movie clip controls, then a mix of the two. Followed by some mathematical scripting, then again mixing it. YOU WILL FAIL IF YOU TRY TO DO IT ALL AT ONCE.