going to need the serial number of the unit to find the correct manual for it.

As for manuals you can go to skyjack's website and get the parts and service manuals for you unit by serial number yourself if you like.
Just google skyjack and its usually on the top of the hitlist www. skyjack. com.

But just to make an educated guess it sounds like it might be a filter, changing the filter might help some and wouldnt hurt but is unlikely it.

It sounds like you have a sticky or faulty valve. If it suddenly just started doing this something has changed it's slow side travel speed.

But i am wondering if you could be more descriptive on the 'surge' diagnosis, does it just jump (take off too quickly) when you first move the joystick? Does not have any slow traveling? Like going to full speed no matter where the stick is?
Or is it just speeding up and slowing down, speeding up and slowing down while driving? (as in surging while moving).