It depends exactly what you want to do. Most modders aren't jacks-of-all-trades. Some people reverse-engineer the game itself. Others create new models. More still play with the battle mechanics and party configuration to change the way the game plays. Some look at ways of taking control of FF7's music. Others want to rewrite AI. There's a lot to do, and lots of very different paths to take.
Still, I think that in any case, the first step is to program. The tools you'll use, disassembly, reverse-engineering and exploiting the knowledgebase will always demand technical proficiency, and the easiest way to gain this is to do a little programming. Even if you only learn to produce basic applications in C++, you'll have already covered memory management, pointers (related to memory), how machines handle numbers, hexadecimals, and the essential info to modify, compile and run other peoples' tools. You don't have to learn about anything fancy, like object orientation or polymorphism. You don't have to know how the code translates into assembler/machine code (though it'd help). You don't need to be writing operating systems before you mod. But having a little coding experience - just garnered over a handful of weekends - will put you on the right path, and get you into the right 'mindset' to understand the tools you'll use.
My two cents.
