Tech is always available (basically). Every day of the event there are inspectors available. Racers need to go through Tech after spins, for instance - so there's always someone there. The crowds are way smaller and the inspectors not so harried - after Sunday.
If you miss the drivers meeting you'll miss the fun of the spectacle, but won't be banned. If you're a rookie on the salt you will need to do a rookie orientation. They're held every day (as needed), too.