It would be cheaper to buy new set. Older brushless uses non-sensored motor and there was no timing advance back in the days. Since LRP SPX and then the Tekin RS boost wars, the technology hasn't changed as dramatic, maybe due to the recent financial meltdown, which strained everyone out of their luxury spending.
If you want a future proof ESC and motor, get one that has updatable firmware. Nothing much about motor advancement now since most timing and boost can be controlled by ESC.
For beginners, a Cirtix 17.5R combo is a good choice as it is extremely affordable. Alternatively, if you want more performance or speed, if you can handle it, go with the latest firmware-updatable, boost capable ESC with matching brand motor (gives less headache when troubleshooting compatibility isssues).