Im an avid weekend angler, that takes my fishing pretty seriously. Ive been running a basic Helix 7 Di unit for a couple years now, and wanting to upgrade my unit to help improve my fishing. I'm looking into purchasing a Helix 9 MSI+ unit. Is this as simple of an install as the unit i have now, or are there more specifics to pay attention or more accessories needed. More of the reason for my question, is i see in the description it specifies select models only. I appreciate any information!