Gas Gauge not reading

I've had a problem with my 92 mx3 for a little while now and i want to see if its something i can fix myself

when my tank gets below about 1/2, the needle on the dash drops all the way to below empty even though i know i've got about 4 or 5 gallons of gas really in the tank.

i've been able to figure out a workaround where whenever i get a fill up on gas, i reset my trip meter to 0 knowing i'll get about 300 miles before i have to start looking for a gas station.

ps-the fuel light does still work warning me when i'm just about to run out but i use the trip-meter technique most of the time since i don't like to get that close to really empty.

any ideas what part might need replacement/service for this? something i could order and actually replace myself?

Thanks
Austin