Is it hard to replace a lower triple tree?

Not really hard if you have a hydraulic press. Its basically drop the forks out (15 minutes), remove the top triple(5 minutes), Remove the lower triple(2 minutes), press steering stem out of old lower triple and press into new triple (10 minutes), reinstall everything (30 minutes)

These times are what it would take me in my garage to do. A dealership should be able to get this done quicker with a decent mechanic.

Haha thats funny because I think my lower triple tree has the exact same piece broken on the same side. If I'm not mistaken, thats the turning limiter right? Basically, prevents the steering wheel from over turning ??

I kinda opted to just leave it be. I don't think it really jeopardizes the safety of the bike as far as riding goes (if anyone can give more input on this, I'd appreciate it!)
Although my handle bar is a tad bent also. Let me know how it goes.

I just replaced mine. It was cake. Still waiting on my Vortex upper triple though and trying to get the damn ignition bolts out.
Make sure to put a light coating of grease on the stem to keep it from pitting since it is aluminum. Also make sure to pack the bearings really good with grease.
I didn't need a press for mine because I bought a used one off Ebay so the stem was still in the lower triple.
I'm not sure how they come from Yamaha though.
The stem and lower triple will probably come as 2 seperate pieces and will need to be press fitted.
The other fun part will be getting the adjusting nut torqued properly.
From there your all good