I installed the HD speedo/tach on my 08 FLHR. It was simply plug and play. My wiring was a little tight, but was do-able. If your year is anything similar to the 08, the original wiring socket will plug directly into the new speedo/tach input. Should be very simple.
The only "tip" that I have is that make sure you cover your rear fender with a soft, large towel of some sort so that you can lay your dash/console on it when you are working on the install.
Hope this helps and good luck.