Do a quick search. There are plenty that have done this in the modify section or projects section. There are a couple digital guages that look real nice next to the factory guages. Many of decided, for the same money, we would rather have an entry level graph. Lowrance X4 Pro is $99 at most outdoor places and works great.
Do a quick search on here for Hawkeye or transducer and you will get a few threads. That will be your bigger decision is if you want to mount a transducer on the transom or shoot it through the hull.
Good luck,