Oh no I only have half my team set in Diamond, and they don't all level match either. And the other half I'm working on in FireRed and Ruby. It's a mess, but I swear I will have them all! XD
I don't use ActionReplay/Gameshark, mainly cause I fear it'll mess up my game too. I also don't like hacked Pokemon, I don't think it's fair. Getting items and whatever for training/breeding is fine by my book, as long as the Pokemon itself remains legit. I'm not hating on the devices or anything, it's your game you can do what you want with it. And I would totally use them to get extra copies of some items but it makes me too nervous haha. I wish you luck. :)
Heh it may take me longer to get there without those things, but I feel more satisfied in the end. Well, I hope I will anyhow. I'm not there yet lol. XD
PS - I hear Action Replay messes up less than Gameshark? Idk, thought I'd tell ya since you seem a little nervous heh. Might wanna poke around online first before trying? *shrugs*