This thread should be in the RVing in Mexico and South America forum.
Many believe Mexico to be very dangerous. I have been to Mexico twice in my RV and loved it.
In 2010 and this last winter in Baja.
There is a sticky in the RVing in Mexico and South America forum that talks about Legal requirements.
However it's is geared to U. S. border crossing. Your Shipping agent should be able to help.
In 2010 I met a Swiss couple in Mexico who had shipped there RV from Europe to Argentina.
Then spent 10 months touring South America before heading north through Mexico.
We have stayed in Manzanillo and then inland at Guadalajara, Loved them both.