You won't have to upgrade any other wiring in the truck to take the big output alternator. Just the connections to hook the alternator up to the loom. Trust me that getting your electrics running solid is worth the effort. When a manufacturer designs a system for their vehicles, it is always over engineered as a safeguard (unless it's some nightmare built in China) so you can be assured you won't get any secondary faults from having more available amperage unless there is an actual existing fault with that part of the electrics. Having more available amperage will improve the starter motor, lights and relays performance.
And as for your local friendly ass hat behind the parts counter - "buy a Toyota?" Really?