Swapping a PCB in a modern WD drive will most probably not work. This is because each PCB stores unique drive specific information in serial flash memory.
You can determine the number of heads using HD Tune.
See http://malthus.zapto.org/viewtopic.php?f=59&t=650
You can match the manufacturing date on the label against the date codes on the PCB and on the chips. To this end, could you upload a detailed photo of the component side of the PCB?
You could also input the serial number into WD’s warranty checker:
http://websupport.wdc.com/warranty/warrantycheck.asp?custtype=end
There are other numbers on the label that could help identify the drive, eg the full model number (including suffix), the DCX number, the R/N number. There should also be a 2061-xxxxxx sticker on the PCB which should correspond to a 2060-xxxxxx number on the artwork, and this number should relate to the R/N on the label.
The width of the HD Tune access time graph should tell you the RPM of the drive. The access time graph for a 7200RPM drive will have a width of 8.33ms whereas that of a 5400RPM drive will be 11ms wide.
See http://community.wd.com/t5/Desktop-Mobile-Drives/Is-this-a-genuine-or-fake-WD-drive/td-p/224428
