I wonder if, when the time comes, if the root system is shallow enough
for me to dig it out myself? Do you have any feel for that?

Assuming there's not a lot of rocks and such, not more than a couple
of hours. It can help if you cut some of the outer branches to give
you room to work, but leave enough of the main trunk/branches to push
and pull with, at least chest-high. Dig near the dripline (two or
three feet out from the trunk) where the roots are smaller rather
right next to the base. Anything too big to cut by standing on your
shovel blade, either chop with an axe or clip with a pair of pruners
(whatever you have that you don't mind getting in the dirt, it may be
worth getting a cheap pair of pruners just for this). Some stuff will
come out with only one shovel depth, some take two or three.

If you don't mind driving on your lawn and have a suitable vehicle, a
towchain makes things a lot quicker, as long as you take the right
precautions, though it is still best to start with at least one shovel
depth around the shrub first. (A jacket or blanket on the middle of
the chain to keep it from flying if the bush breaks or the chain comes
unhooked, attaching to a tow hitch or frame rather than the bumper,
going 1-1/2 times around the base of the shrub to form a loop that
self-tightens, not "popping" the chain but bringing up the tension
slowly until the tires just start to spin, going back for more digging
and chopping for anything that doesn't come out on that first pull
rather than trying to force it,...)

A friend with a backhoe usually just asks "you wanted it where...?" as
they dig it out of the ground. If you can afford it, renting or
hiring one is by far the easiest way.

Caveat: my soil is pretty sandy and easy to dig, YMMV.

--Glenn Lyford