I bought a JP trigger to replace the pretty heavy stock one on my M&P15T.

I read through the docs before I bought it, and it looked pretty simple to install.  After watching the video, though, it looks a tad more complicated; not so much the driving out of pins and adjustment of allen screws, but the metal removal involved in the disconnector timing and the fitting for the safety involves tools I don't have.

The included video recommends using a bench sander (which I don't have) for these operations. Will ordinary stones work for this?  I don't mind investing in a couple of them.

Because JP is located in town, I can ship the lower to them for about $6 and get it back in a week and know it was done "right", although the idea of doing it myself is appealing, if anything to see what's involved.  Its probably a dead even exchange in terms of money, with the stones probably being a little cheaper.

I'm pretty mechanically inclined (I load for 6 handgun calibers on a Dillon 650), so it can't be that difficult for me, but I'd hate to fsck it up and need to buy another trigger...

I thought about doing mine myself as well but am glad I sent it in. If it were any other trigger I'd say go for it but in this case I'd send it in.

If you're mechanically inclined, you should be able to handle it no problem.  Unless I'm mistaken, new triggers come with an install CD also.

As far as metal removal, go with stones.  They're far more precise and forgiving than anything power driven.

They come with Locite on the screws, but make sure it's there.  I had a JP adjust screw creep out and lock up my trigger assy a few years ago.  It was a used trigger I installed, so the old Loctite remnants weren't enough to hold.  The new stuff is holding still.

I did two... piece of cake if you have basic mechanical skills.

I've done two as well now.  JUST finished one on my new DPMS LR 308 I picked up today.  I have yet to need to grind or "stone" anything.  Both of mine have been adjustable to the right specs out of the box - YMMV

already did one and am getting ready to do a second.  They aren't that hard to do as already stated

Very simple, get a file and take your time.

You can install it yourself, though tuning it correctly could take 10-30 minutes, depending on if you've done any adjustable triggers before.

JP does prefer to install them himself though, then he knows it's done right and that you'll be happy.

+ 1, cant hurt