There's nothing wrong with that bass. The best upgrade you could make is with the strings. It will make the world of difference depending on the tone you are after - slap / cutting punk, try steel rounds - punchy blues or R&B, go for heavy flats. The difference will be night and day.
Don't waste you cash on bridges, tuners, pickups - you've got a good bass there, the difference those changes will make will be minute, especially in a band mix.