You don't so much have to worry about getting tuners that are larger than your exhisting holes... the holes can be bored out within a matter of minutes without having to worry about hurting your guitar.... the only way to fit tuners that are smaller than your exhisting holes would be either to find retorfitting ferrules that shrink the hole size.... or plug the holes with maple and redrill (not recommended). The only concernt that I would have if I were you is the location of the mounting screws on the back of the headstock... you don't want those little babies sticking out if you have to change the configuration... look for some tuners with a similar mounting configuration and atleast a larger required diameter and you'll be fine. If you have to end up drilling a bit... heres some luthier tips!!!

1. Always drill into the surface that is lacquered or finished... never out of. In this case you'll want to drill from the front of the headstock to the back of the headstock since the holes in the back should be coverd anyway.

2. Use masking tape to prevent chipping of finishes. You'll want to place a line of masking tape that goes over the 6 holes on both sides. this keeps the wood from flaking and holds the lacquer a little more firmly.

3. Careful when pulling the drill bit out. Always keep the drill bit spinning when pulling it out of the hole... Stopping the drill bit and pulling it out will result in the finish being snagged and chipping away around the hole.

There you, its as easy as that. Nothing really to it