Answers:
1) you now own a 4th gen Runner
2) it depends on whether or not your Runner is a 4x4 vs. 2x4 as the 4x4 on the V8 will probably require transfer case lube change. Also, the V8 has a timing belt that requires changing at about 90k miles.
3) you made an awesome choice by getting the V8. Your Runner will bring you years, and tens of thousands of miles of pleasure and fun! Joining this forum was brilliant on your part as this will become your #1 source of information/advice on maintaining/modding and wheeling your Runner!