The schematic shoudl tell you what kind of pot to use as far as what resistance it is... If it's a humbucker setup, which I'm fairly confident that the Washburn X-Series uses buckers... you're going to want to make sure your pot is a 500k pot.... You can use a 250k or 1meg but it will sound differently than it did with the stock pot in...
Also... Always use linear taper pots for tone pots... The difference between the two is that the Linear taper has an equal band of reduction across all settings... Audio taper pots have an exponential rate of change.. meaning you'll notice a big differnce in change from 1-6 and very little change from 6-10...... Always use linear for tone... and audio for volume.