You'll be fine
I did the TAT last year on a DRZ400 and I met inmate Backlash on the last day on his '13 500EXC. He did the entire trip and changed the oil a few times. No big thing. Three drain plugs (all 13mm), easy air filter access.
I bought his EXC a few weeks ago and maintenance isn't a big deal.
Go for it! This bike is special.
I'm an asshole and I approve this message.