Temporary vehicle import permit

Renew Temp Vehicle Permit and tourist visa

Hi,

Does anyone know if you can renew your tourist visa and your temporary vehicle permit in Mexico without crossing the border? We have heard that it is possible to renew a tourist visa at an immigration office, but we are not clear if you need to do so within 30 days of your visa's expiration date or not? We have also heard that if you change your visa status you need to contact aduana within 14 days to extend your temporary vehicle permit. Has anyone tried renewing their visa and vehicle import permit while in Mexico? Any advice is greatly appreciated.

Thanks