i think a standard rebuild would be pretty pointless
you wont get any more power out if it
if your turbo is stuffed then for a cheap upgrade you can buy a r33 turbo. make sure you get the inlet elbow and oil and water lines. the standard turbo can be used for about 150rwkw while the r33 one can out out about 180rwkw
r33 trubos sell for about $250-$500. but if you want something better you can spend about $1300 on a hks gt2530 which will make about 200rwkw. however, you need a decent fuel system, front mount etc