So, the first you can do is should the height of your pickups. Relatively easy process you can do on your own and you wont ruin anything at all. Get a screw driver and adjust the screws next to your pickups. youll have to take off the pick guard to access the neck pick up. It's really a preference thing. The higher the pickup, the bassy-er, the lower, the more treble. BUT once you've done you, you have to play between the pickups, because by doing so, you can alter the volume output, and so you have to tinker and find the balance between them volume-wise.

The next option is changing the caps and pots. Rather than trying to explain it and get it wrong, go here and it's got a real good explanation with tone clips. It'll alter the way you cap's work and the tone roll off.

There isn't a good p-90 style tele pick up, but I threw in Lollars on my tele: Vintage T in the neck for that old-school, thicker tele tone and a J-street in the bridge, which is bit "throatier" and less twangy than a normal tele-pickup. it gets kinda close to a p-90 range. I really really like the way the J-street sounds as a tele bridge pickup. I hate tele bridge pickups... too twangy. The J-street is a special order, but it's no more expensive than their other pickups. You just have to email them and ask for it.

I'm sure a quick search around seymour duncan and diamarzio's websites will give you a better idea for the more "consumer priced" range... although my "botique" tele pickups were only like 110 each if I recall.

I'd suggest just having a tech install those mods, just easier, and not too pricey.

Also, one time I went on this tele forum called Tdpri.com and mentioned I was looking for a wiring scheme so I could blend the bridge pickup with the neck pickup using the tone knob. I never got around to doing it. I liked my lollars enough, but it was a reallllly cool thing, and someone drew me the schematic really quickly.