Hey guys, i recently bought a John 5 squire tele, with the prospects of doing it up. However, when reciving the guitar i noticed it has what i believe to be a bad earthing problem so it hums badly when the metal isn't being touched and it gets what can only be described as microphonic feedback at loud volume levels (band practicing level).

I figured since i'm going to sending it to my local tech why not wait til i can afford to do it up and do all the electronics at once? So i'm about to order new pots and pickups anyways and i just wondered if the pickup switch made any difference what so ever? Is it worth buying one whilst i'm getting pots and such?

In short, do pickup switches make a difference to anything?
yes they can, the more espensive ones normally bring silent switching with them, which can be handy for gigging
The only difference is how they feel as you move them. Some people like stiff switches, other people like loose ones, some people like their switches to spring and click into position and others prefer it to smoothly glide. Which switch will feel best for you is really just up to you to find out, though any decent brand like Switchcraft, Oak Grigsby, Fender or anyone else along those lines will be decent in terms of quality. Tone-wise, there's no difference.
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the switch should make little to no difference in your sound. bad grounding shouldn't cause feedback, but i'd take it apart to check for loose wires or bad solders. if you're having feedback issues at high volumes, i'd say its more likely that you're standing too close to your amp or facing the amp when you play. as for it going away when you touch the metal parts, thats fairly common. strats and tele's are just prone to buzzing, and you can ground it through yourself by touching the metal that the electronics are grounded to.
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Yeah of course they do... Get some decent dimarzio's in... Squier pickups and epiphone pickups are all bollocks...
The alternative thing to do which would be just as good (and cheaper than new pickups)... Get a decent noisegate... That reduces hum and natural feedback from any guitar
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I was replacing the pickups to make it better tonally, not to kill buzz or anything.

To the comment about feedback, it's not feedback from standing to close or using too much gain or anything, as it doesn't matter where i am, also it's not regular guitar feedback, it sounds like the feedback you get from microphones. The only similar case i've heard is when my friend got a new epiphone which pickups wasn't waxed even though they had covers on them. This isn't the case with mine however since they are not covered.
get a killswitch !

the switch itself shouldn't really make a difference. It might be prone to break easier than a more costly aftermarket switch.