I bought this guitar several years ago and I think I'd like to change the neck on the guitar. 1st of all I have smaller hands and am thinking of getting something with a shorter scale length and a smaller radius. I've also never really been able to use the vibrato on the guitar. Not sure if it's the roller nut or what.
I don't know much about where to find a neck that will replace mine or even how to go about doing this. Does anyone have any advice or suggestions?

You cant change the scale of the neck. Doing so means you would have to move the bridge nearer the neck pocket, or you'll never get the thing to play in tune. All your intonation will be off.
A shorter neck radius won't aid you either. That will just increase the curvature of the fretboard.

_________________
No no and no

Niki is right: you can't change the scale length of the instrument. What you can do, however, is get a new neck which retains the 25.5" scale but has a slimmer profile. Some find that a smaller neck profile makes an instrument easier to play. Others will disagree and state that big necks are easier, but it's a matter of preference. You could go to a shop and try a bunch to see what you like.

As for the tremolo, is it possible that you either (a) have too many springs in the back cavity; (b) lost the spring that sits underneath the trem arm? You can check by unscrewing the back plate and verifying how many springs are present. Three is standard for either a one-way or floating bridge, but many people put five in and tighten down the claw in order to make the guitar a "hard-tail." Setting up the trem can be somewhat finicky, but Fender has a reasonably good guide on the website: it's located under the "support" tab in "how-to guides."

Though to add a little to what my esteemed colleagues have said, if you really want a shorter scale neck on a Strat it is possible to buy a "conversion" neck. Warmoth do one, which will convert Fender's 25.5 inch scale to a Gibson-like 24.75. It is engineered to work with the body the way it is, without need to move the bridge. Here it is:

http://www.warmoth.com/Pages/ClassicSho ... Conversion

Against that, I suspect this doesn't really address the issue of smaller hands. I have comparitively small hands and notice no particular benefit to playing the 24.75" scale of my Les Paul. It is not the distance between the frets that is the issue so much as the carve of the back of the neck.

I'd suggest HMNyge goes to a shop and tries out an American Standard Strat, which seems to come in a moderately "fast" (thinner, front to back) C-shape carve than some other models. And to really get a feel for these things, also try out an Ibanez with one of the thinner Wizard necks. Or something similar by several other makers - any guitar neck aimed at shred-type players tends to be slimmer.

And in case it isn't clear, the thickness of a neck concerns its dimensions front to back - the distance between the surface of the fingerboard and the middle of the back of the neck. We're not talking about the width of the fingerboard from bass to treble. Give or take a millimetre or so that measurement stays pretty much the same on most electric guitars.

Any help?

Cheers - C