I wouldn't go with that nut. I would get the unslotted one, and have a pro install and slot it for you if you can't do it yourself. The thing is that your guitar has a 9-1/2" radius, and that nut is for 7-1/4". If you use that nut, you can lower the middle four string slots to the proper positions for your radius (it's only a slight change). However, your guitar – if it is like any MIM I've seen – has a 9-1/2" radius curved-bottomed nut slot. So if you use the nut you mentioned, you end up having to trim down that center post in order to get the nut seated. Not only is that kind of a pain in the ass to get absolutely perfect, but it means that the bottom of the nut is only contacting the bottom of the nut slot at three small areas. In all honesty, that probably isn't a problem tonally...but it still just doesn't seem right to me. It's just not how a nut is supposed to sit, by traditional standards.
You can get the unslotted blank with a 7-1/4" curved bottom, or with a flat bottom. The 7-1/4" will have to be re-radiused a little bit on the bottom to match your nut slot. The flat-bottomed blank will have to be fully radiused. The flat bottomed gives you more meat to work with, and more room for error. The curved-bottomed must be re-radiused very precisely, without taking off too much, or else the top of the nut will sit too low.
As for other mods to MIM Strats, IME the most important are to junk the whole bridge/saddle/spring/claw setup and get something well made instead. Callaham or Hipshot are my personal favorites. The next most important thing would be to get the frets leveled, crowned, rounded over, and polished. The bridge/vibrato, nut, and fretwork are the worst areas of MIM Fenders IME. Other than those areas, they're quite good.
After those most important things, I'd go for pickups (stock pots, switch, jack, etc. are usually fine unless you want to change the values or tapers), then tuners. My favorite tuners for MIM Strats are Hipshot lockers with the small oval buttons (you must order the buttons separately). However, Schaller for Fender lockers will drop right in, and they are just as good as the Hipshots (but not as good looking IMO). Also, since Hipshots are based on Schallers, you might be able to fit the ovoid Hipshot buttons onto the Schallers, as long as you use the stock Schaller button attachment screws; I haven't tried it myself, though. That said, with a nice bridge and nut, the stock tuners are really quite serviceable, and they are the last thing I would worry about upgrading.