The full path is is only required if the file or the sub-path isn't directly off of the mIRC directory. Your dialog is quite well laid out. Pay attention to the dialog commands and their formats as specified in the help file, as they are picky about getting it just right.
I suggest that you just do it a little bit at a time and get each part working, then we worry about combining everything.

If you want to use hash tables for the storage, I strongly recommend that you read up on them before starting to try to code with them.

If you're already familiar with using text files or ini files for storage, you can start doing it that way, then I can show you how you cna use hash tables with the files that you've already started.