Tachometer, 1999 Ford F-150

I have a 1999 Ford F-150 to which I wanna install a tachometer. I have found one that I want, and at a good price. The problem is, that I e-mailed the company, asking if I would need any other accesories, or if it would even work on my vehicle. HE said that the possibility if it working, were 50-50. He said that It would work, but as to what nature of acuracy it would read, he wasn't really sure. My question is, has anyone installed an aftermarket tach on a Ford truck, or any vehicle for that matter, and how hard was it, did you need any additional accesories, and finally, did it work well enough? I am very intrested in buying the thing, and trying to install it, but I don't wanna waste all that money, on something that isn't going to even read right. So please if you have any suggestions, I would really appreciate them~~jp

Tach wire: on the 4.2L it is a dk. blue/lt. green at the coil pack on top of the motor. On the 4.6L it is a pink/white in a 3 pin plug at the front of the motor below the air intake and next to the fan. On the 5.4L it is a lt. GREEN / WHITE at the coil on the passenger side of the motor between the fuel injectors.

Thanks Blazeronspokes!! Ok, sounds simple enough, I think. So do i just tap into the dk blue/lt green wire with a lead from the Tach and then ground the tach? Is it really that simple of an install???jp