I got into the habit of annually repacking the bearings on our old tent trailer, so I've continued on with the r-pod. Including the time to pull out the tools, cleaner and grease and jacking up/down the trailer, it takes me two hours to do the job. You'll also want to adjust your trailer brakes at the same time (unless you've got the newfangled self-adjusting brakes).
As techntrek said, you'll need new bearing seals (about $2) - the old ones must be destroyed to get them out.
Personally, after looking at the inside of the r-pod's hubs, I don't see that squeezing grease into that zirc fitting would do much good. You'd have to fill the entire void with grease before it started pushing the old grease out the bearings. Even then, I'd be worried about getting grease on the brakes. But, on the other hand, the zirc fittings are there for a reason and others think that using them is perfectly legitimate.