Write a plugin with personalized media upload

Hi all,
i’m writing a plugin that need a special media uploader.
It must upload some files (of various type) , check if my_store_directory is writeable, than upload using ftp layer.
So, the question is : how can i use internal wp classes to
– check filesystem permission
– check possible upload method (ftp, ftps etetcc)
– manage uploaded file and put it on my browser protected <my_store_directory>
Off corse, i can read the code in class-ftp.php (and highter version of it), file.php and similar.
But it’s not very simple…
There is someone know how to do it in few step, or can give me a URL of some interesting post speaking about that ?!
Thank’s