I installed a speedo-healer on my 06 a few weeks ago. They do make a plug and go so the only splicing is to get into a power source. Other than that, you just need to push a few pins out of the big grey connector and put them in the harness provided by speedo-healer. Took me about an hour to install (I'd recommend removing the tank.) I ended up mounting mine under the seat, because my PCIII is under the passenger seat compartment. But, I'd actually suggest you look for a better place to mount it so you can get to it easier. I also programmed mine to run at -12%. I run the stock tire and also have 16t front sprocket. The instructions on programming are pretty complicated (for me anyway), but if you follow them exactly, you'll be pretty safe.
As for the top speed, There's only one button on the speedo-healer. Just push it once and the top speed will display on your odometer (power turned on of course). If you hold that button down for a few seconds, it resets your top-speed.