I've gotten so much use out of this pic ...
Here's a comparison of the 3 shifters being discussed. Keep in mind that the TWM is their older generation, but the new one is fairly similar for length. The length of the shifter
below the ball is what determines the length of the shift, and the length above determines the height of it. From what I read, nobody's been dissatisfied with any of them, so it's a safe bet whichever route you go. They all have their strong points: Kartboy with the package deal for shifter, bushings, and knob; B&M replacing the plastic boot that the ball of the shifter sits in; TWM having ball bearings at the bottom of the shifter. They're all good, it's just a matter of preference.
As for the install, I can't stress enough that you need a set of hog ring pliers! That's what you use to get the snap ring off, and even with the right tools, it can be a pain. If you get the Kartboy bushings, just read their directions and you'll be fine. Just remember that the stock is one piece, not 2 like the urethane ones from Kartboy, and use the bolt that it comes off of to push it from the metal ring that it's in.
Search around before you do the install - there's tons of info on here about it.
edit: Oh yeah, That's a stock
P5 shifter that it's being compared to. Here's a pic of the stock MSP shifter compared to the TWM: