Need Help With Fuel Gauge Problem
 

2000 Boxster S with 152K on the clock. Purchased the car January 2019 and noticed a problem with fuel gauge. When I would fill the tank the gauge would never read full. The indicator would read just above 3/4 and never read full. As I drove the car, the indicator would drop down as it should. Yesterday I did a 400 mile trip and noticed the gauge is now stuck just above the 3/4 mark and is no longer moving down as gas is consumed. I used the trip odometer to watch my miles to make sure I wouldn't run out of fuel. I did some research and it seems fuel gauge issues can be a sign of a faulty fuel sending unit. Is there anything else that can cause fuel gauge issues or should I start with replacing the sending unit? Thanks for any and all suggestions or input.