2007 Lincoln Navigator cutting out

I have my brother’s navigator. It has started cutting out a little on inclines. Ford dealer wants $85.00 to hook it up to a computer to check it out, then who knows what it would take to fix it… I need to drive it 300 miles to give it to his daughter ( he passed away in June ) I afraid I’ll be stranded if I try the trip. Could anyone help me with posibilities. What could it be? I drive it about 30 miles a week, otherwise it stays parked in my driveway. What do you think? Should I try the trip?