Hi Billy and welcome to the forum.
No need to retune the engine although if this was something you wish to have done, the free flowing exhaust would allow a few more horses to be unlocked.
As for the gear/diff oil this should be changed as part of the major service which is every 3 years from memory.
TBH if it were me I would do it every 3 years or 36k miles, whichever comes first.