I've never done it myself, and that's probably because I only own one electric and am not really technically inclined the way a person needs to be to do this kind of thing.
That being said, from what I've read, changing pickups in a guitar is not terribly difficult for anyone that has basic electrical wiring skills. I think a big part of the difficulty depends on what kind of guitar you're doing it to. I believe Les Pauls are more difficult than some other models. Your Telecaster might be more simple.
Try these forums because I'm sure somebody there could tell you all about it:
I found the pickups I'm gonna put in my tele. They're pretty amazing and give you the option of single-coil, p-90, and humbucker (in series and parallel) with pull pots....
Holy shit, those are the same pickups I plan on putting into my Rogue HH. I want to get a 10-way switch or something so I can have every combination imaginable.
Right now I'm debating taking the stock pickups out of my Epiphone LP and putting Burstbucker Pros in it.
Yeah, I'm just gonna do the pull pot thing since my Tele only has one volume knob and one tone knob and I don't want to drill any new holes or anything in case someday I put in other pickups or something. I think there are only 4 options for the usage of each pickup, though... unless you want a selector that controls the usage of each pickup AND which pickups are active. I'll just use my normal 3-way switch for that, though. But I'm excited--this guitar's gonna sound huge through my ac30 now... especially since it's semi-hollow. Come on, tax return!