It does still have three trains, however the third one is currently being redone or in standby in case one fails or for extra capacity. Train 1 was recently overhauled and I *think* Train 3 is currently the other one being used, whilst Train 2 is currently in the maintenance shed.
I'm currently 16 years old too, and I wish you luck on becoming an engineer on Stealth (and other rides too for that matter)
Don't have any experience working with Stealth, other than the fact that I've ridden it and it's a nightmare in terms of reliability XD
(That being said) has there been any action today...?