Hi rwilson,

Do I need a special interface to connect the Lassen SQ to PIC16 even itīs working to 5V?.
Yeap, you do need a MAX232 like, level shifter. BTW , the IQ version is better.

Do I need a backup power to conserv NMEA protocol as default?
That is an Yes too if you want to keep the module settings, including NMEA sentences, NMEA protocol, and Serial comm port settings.

Good Luck