Yes, easy enough if you have the know how to replace stuffing properly. If not, have someone show you how the first time. I do mine in the water, since you can't adjust them properly until the boat is . . . in the water.
When you take the packing nut loose, there will be a significant amount of water coming through the shaft log tube. You can stem the flow to a trickle by packing some old rags around the shaft and into the tube. Probably not a wise choice to run for parts when its in this state. It may take you a while to dig out, then cut and fit the new packing, so make sure your bilge pump is up to the task and you have the correct size packing on hand.
Careful . . .I Have a Generator and I'm not afraid to use it !