Since you've already got it, all of the normal discussion about how to get a good rig is probably not helpful.
Here's what I would recommend for conversion steps:
1. Fix. Every. Leak.
2. Wait for it to rain, then Fix. Every. Other. Leak.
3. Add one 100 AH battery to your battery bank (you probably have two that run the bus and chassis). Put it on the other side of an isolator. Now you have basic juice available when the bus is turned off. You can connect an electrical system to it at any point in the future, and you won't accidentally get stranded because you drained the batteries.
4. Research this skoolie forum by topic: a)basic electrical; b)plumbing and c) maintenance. Ask questions on the various threads if you have them. People will happily answer.
5. Delete your Facebook app, or at least stop subscribing to the crappy skoolie conversion facebook groups. They will frustrate your journey, mislead you or piss you off.
6. Write out a plan and calendar to do preventive maintenance religiously, put in a very basic electrical system and a quick 'n dirty freshwater, sink, and graywater. Plan well, but shoot for passing with a D- (minimum viable product).
7. Look at your other priorities in life and make sure you are good with taking up to a year to get your conversion done.
8. Start to drive the thing. Do overnights and weekend camping trips, and TAKE NOTES IN A JOURNAL about what works, what doesn't. Learn from your experiences. Watch the expression on the faces of your kids for guidance.
The rest will naturally happen on its own.