What will I need? Tools, other purchases, etc. Also, how do I install?

Welcome.

You'd have to remove or extensively loosen the strings, remove the pickguard screws, lift and swing the pickguard out; disassemble the existing bridge pickup from the pickguard, all which involve the proper sized phillips head screwdriver(s); you'd have to unsolder the original bridge pickup which requires a soldering iron and skills to do same, add a small drill hole in between the two existing height adjustment screw holes on the bass side of your pickguard which also means you'll need to have and have experience with a drill and the proper sized bit, making absolutely sure that the drill is no where near any of the pickups or the activated motor from the drill will demagnetize your pickups; mount the JB onto the pickguard using that newly drilled hole for your bass side mounting/height adjustment screw (don't forget those pesky springs); wire up the JB which again, requires a soldering iron and now, solder and skills to do same and of course, follow the wiring diagram which comes with the JB; you'll need a small piece of electrical tape to insulate the red and white wires of the JB which you'll have to solder together. In your particular situation, being that the guitar is a MIM, the two single coil pickups will be reverse phase to the JB. This would require you to reverse the black and green wires of the JB per the wiring instructions. Then, you'd have to test your work and premising it is all a 'go', reattach the pickguard to the body, retune the guitar and then adjust the JB's height for optimum performance. Lastly, you'd have to synchronize the pickup's magnetic flux with the other two.

And that's pretty much it.

_________________
You dig?

Like Martian said,pretty much it...simple,eh?

Nothing to it!

I didn't even get into the aspects of with all the strings being lax or off, the tremolo block or even the entire guitar may have to be setup again upon restringing to pitch. This too, 'a piece of cake', as it were.

_________________
You dig?

Exactly,I think people read about pickups and other mods and really don't have a clue where to start,or what the results will be or what else it will change.A Strat is a good guitar to work on,but they're not immune to blunders by inexperienced "techs".

From what I've seen, Strats are some of the best breeding grounds for the inexperienced to create and multiply blunders. This is all because they don't realize all the above as part of the process. All they equate is merely installing a couple of screws and soldering a couple of wires and when they find out what a pro will charge, they get all indignant and this is when they attempt to do it themselves or have a 'friend' do it. Yet like I've said a million times, that's even more money for the competent tech down the road when (s)he has to undo the mess and ultimately (re)do the job correctly.

_________________
You dig?

I have a Roadhouse Strat. Ive got a JBjr in the bridge and Love It. Get the jr and save yourself a new pickguard.First get a towel and a small pillow or a rolled up towel for the neck to rest on. Remove the strings, remove the pickguard. Carefully flip the pickguard over and remove the bridge pickup from the pickguard. Unsolder the pickups Ground and hot wire going to the switch.Install the JBjr into the pickguard. Then, I think you have to solder the Red and White wire together( if you are NOT running a coil tap) Black is ground, Green to switch. tie your wiring up neat, put the pickguard on and restring it. Should take 45 miniutes and the JBjr sounds really good. You can play AC/DC tunes and it sounds pretty convincing. Hey, give it a shot, It's just a guitar, It's not Brain Surgery, and its a MIM not a '62 strat. Thats the only way you are gonna learn. Good Luck Dude. Oh, All I used for tools was a soldering iron, thin solder, phillips screwdriver, wire cutters and black electrical tape. remember to put a light coat of soldier on the wire ends before soldering them in place.