at 18k kms, i am pretty sure you dont need a tranny fluid change or a diff fluid change. not yet at least. i just changed both of these at 38k kms. and when the fluid came out, it looked almost like new.
anyway, nothing else you need to do. good that your battery was on a tender, thats all you need really.
Current: 2013 F10 M5 & 2013 GLK350
997.1 GT3RS (gone)
2009 WRX STI (gone)
e92 M3 (gone)