G'day millzzy. It would involve a firmware hack. The nag screen 'Your device are currently configured for Automotive mode ....' also appears on dezl 560 and nuvi 465 ['truckie's nuvi']. One of our Navigation Software Experts would be up for the job if they have the time.
However, if you don't use the truck mode functions at all you could just flash it with nuvi 2797 firmware. It's possible to do that in 2 ways, complete flash using full 2797 fw, or hybrid using 760 boot.bin combined with 2979 FW1_resources.bin & fw_all.bin. The latter is safer and retains the original dezl 760 HWID of 1516 but it would function as a 2797 regardless.