[IneedHelp]

Good job! The only mistakes I saw:

You don't need to include file.inc, it's already included on amxmodx.inc

You aren't using multilingual on the client_prints so you have to change this..

client_print(0, print_chat, "[AMXX] %L", LANG_PLAYER, "custom_maps.cfg exists")

For this:

client_print(0, print_chat, "[AMXX] custom_maps.cfg exists")

The same with the others client_prints too..

Suggestion:
Use the new file system..I think that is faster
Create the file if doesn't exists and write a example on the top of it