Does the driver and navigator in a comp safari need an msa licence, or just the driver?
For comps - the driver needs a competition licence (for the scottish comps - a clubman non-race licence is sufficient), the navigator just needs a club membership card [of an invited club]
For Hill Rallies - both need competition licences (grade depends on the grade of Hill Rally)
and how does scrutineering work, do we need to get someone to look at the motor before or is it checked on the day?
Vehicles are checked on the day.
If it is a new [new-new or new-to-you] vehicle, or one that has been modified quite substantially, I would advise that you get a scrutineer to give it a once-over before the event - if nothing else than so you have the peace of mind that there are no obvious issues before you arrive.
The blue book isn't making any sense to me anymore.
Did it ever?