Welcome to the dark side!
You're off to a good start. Watch out. It can be addictive and expensive if you let it.
Better give that bike butler a good talking to. MTBing can be strenuous. You'll need all the water you can drink. A camelbak might be a good idea if you start doing longer rides. There aren't too many convenience stores out on the trails.
BTW, unless you actually plan to ride that bike on the road in the dark, get those reflectors off those wheels before someone sees them.