I'm not sure if DonP does installations...but he certainly makes and sells one of the best MOSFETs available. The Triggermaster III is so good (check out Don's website Unconventional airsoft...it's a link under the menu News/Info, 5th one up from the bottom)....there's TONS of features in it...but even the defaults work just peachy.
Wiring it up is a snap (sometimes your burned out switch can still be used...but if it's wonky, then don't bother).
Basically there are 6 wires that connect to the unit. +ve and -ve from the battery connector go in one end. +ve and -ve go straight from the motor to the other end. One "gate" wire goes to one switch connection...the other goes to the other and on an AK, where the solder points are on the outside of the mechbox...you don't even have to crack the mechbox open. Getting the wiring lengths and shrink wrap looking tidy is the fiddly part.
If you're not comfortable with doing it yourself...get a good local guy who's comfortable with running wires do do it for you. Don's always been a great help as well...there's plenty of pictures/instructions on his site.
Whether or not it's worth it for your Kraken...that's totally up to you. Even if you eventually ditch your Kraken and get another/something else/etc....you can always take the MOSFET out.