Outdoor Hydrant

My Woodford Iowa 205C outdoor hydrant "variable flow" is now a steady flow, as in more than a big drip.
I've done a fair amt of DIY indoor plumbing, but not sure where to start with this unit.
Should I just start taking it apart? I'm assuming I want to replace the whole unit.
ANd what precautions should i be taking with the long pipe, if any?
It is probably 31 years old. It has dripped in past, but usually just adjusting the flow gear and turning on and off has stopped or minimized it.
The aspen trees are probably loving the extra water, but i don't think our pressure tank likes it.

31 years old? You got your money's worth out of that one. Probably time to replace the hydrant but, it may only be the rubber disc that needs replacing, if you can get to it.

Thanks valveman. Found a parts list for Woodford Iowas BUT no RUBBER DISC is listed.
Just these:Rod Stem, Upper Link, Reducing Coup. 1 Valve Body, 3/4 Valve Body
Packing Nut, Packing, 3/4 Wood Plunger
1 Plunger, 1 Head Assembly 3/4 Head Assembly Lower Link
Iwant to replace the whole thing. Do I just start taking bolts and parts off and then crank the Head assembly off with pipe wrenches?
Any SPECIAL PRECAUTIONS for the long pipe going into the ground??

If it is leaking around the shaft at the top, then new packing is what you need. If it is leaking out the hose, then maybe the wood plunger will solve the problem. If it still leaks, then you will have to go into or replace the lower head and assembly.