I have seen the blower online ( just do a search as many different Mustang performance parts places carry them ) Try Haney Motorsport. Casey has incredible prices. I have seen them all the way down to $4,799 at a couple of places, I just can't remember exactly. The blower kit comes with everything you will need including the new Saleen tune for the S/C. The only thing is a lot of tuners have noticed that Saleen's tune that comes with the blower can be improved on. That is why Kpribble mentioned that he has a custom tune (JDM ) or any custom SCT tune for that matter. Most places charge right around $1,000 for the installation of the blower. So....
Saleen Series VI supercharger $4600-4999
http://www.haneymotorsport.com/Monthly Saleen Sales.htm
Notice who's car is at the top of this web page^^^
Installation - $1,000 although most places that know what they are doing charge around $900 so that really just brings you a bit over $6,000 with installation of the blower and if you purchase the blower out of state you can avoid paying tax.
The reason Kpribbles total bill was around $7,000 is that he added afew other goodies that allow the blower to work really well, 90 MM MAF ( mass air filter ) Lightning as in the Lightning pickup, 39 lb injectors ( higher flowing fuel injectors ) and his Steeda cold air intake, although you can go with a slightly different combo if you wish.
Honestly Cindy if you love the car just go out and buy a non supercharged version exactly the color and way you want it. Then when you get the itch go out, make your blower purchase and fall in love with your car all over again. Just save you minor parts that you replace with the blower in a box so when and if you ever decide to sell the car you can bring the top of the motor back to 100% stock ( for all of the those collector guys/gals ). You wont hurt the value of the car by adding the Saleen blower in the future.
Good luck.