1840 Case Leaking Control Spool on Tandem Pump

Control spool on the tandem pump is starting to leak oil pretty bad. I replaced the o-ring but it didn't make any difference, oil still comes out from around the control arm and runs down the case of the pump. I found a replacement spool online, but it is for a 1845 case.

http://www.loaderpartssource.com/case-1845c-skid-steer-drive-pump-control-spool.html

The picture looks like mine, but I am not sure if it is the exact replacement. Also, should I just replace the shaft...

1840 Case Leaking Control Spool on Tandem Pump

1840 Case Leaking Control Spool on Tandem Pump