Has anyone replaced the piston rings on their vehicle? If so, is it a hard process? I've replaced the injectors myself so I thought maybe I can do this also or would it be better to take it to a mechanic. :D

The physical replacement of rings is easy, but usually is done during a rebuild when the cylinders have been honed or bored. Replacing piston rings, and leaving the cyl. wall finish alone is not a good idea, the rings won't seat properly, and the top ring could be damaged or cause damage if it strikes any ridge present at the top of the bore.

Do you have a specific problem you want to fix? Low compression, etc.?

That is not some thing you normally do your self.
It will take more then a weekend that is for sure.

It isn't too bad, but you pretty much have to tear the engine completely apart to do it. It can be done with the engine in the truck, but is much easier with the engine removed and on an engine stand.

Has anyone replaced the piston rings on their vehicle? If so, is it a hard process? I've replaced the injectors myself so I thought maybe I can do this also or would it be better to take it to a mechanic. :D

In just about any diesel, the top piston grooves will wear out before the rings do. And, if you put new rings in worn piston grooves, the rings will leak and eventually shatter. Years ago, we used to rebuild pistons - but it's not worth it anymore. It's all pretty moot anyway - the top rings used in the 6.2 diesel are hard. If they actually wear out, so will the pistons and cylinder bores.