I did look this one up and found a thread from 2 years ago about it, but I just wanted to make sure that basically my easiest option is to take the wheel in question to a shop for them to put new cone washers on, plus a new axle??

Is there a way for me to measure the sizes of washers and hollow axle I need and order everything online? or is this probably too much work for someone just starting out with bike wrenching?

You need to match the diameter and thread pitch of the axle (if you can match diameter and thread pitch the washers and cones you have will work) plus you need to know the correct length (obviously it will be shorter than the solid axle). If you are comfortable measuring this, measure yourself and order online. If not, hit up your LBS.

that's no huge feat for even a newbie. you just have to have the cone washers and axle...though i'm not sure how to tell you to measure it. one option is to take it to your LBS, buy the parts with them but say you'd like to learn to do it yourself. they should be alright with that, you're still giving them business that you wouldn't have if you had ordered online.

watch out with when you install the new axle, you'll likely need to repack the hubs. actually, for a new wrench this may get a bit involved... i'm really not sure.

Another easier option is to simply replace the securing nuts on each side of the hub with threaded cam devices. They take only a moment to install, are much cheaper than a hub conversion, and don't require alteration to the interior working/cones/nuts/bearings of the hub.