Not sure what kind of boat you have but I do all of my own work, that way I know how it is done. I just finished installing a 3rd unit, power switch and fuse block.
Do your homework before hand, be prepared to screw up something and get after it!
One note, use brass locknuts on your stainless fasteners, they will be a lot easier to remove if you have to do so, I speak from experience!!
Or just use anti seize which is ALWAYS recommended for stainless to stainless fasteners.
Its good to do it yourself there will always be future issues and knowing where to look and what to shake or re fasten will keep you fishing...