New to building ARs. The M5 come with everything but handguard and stock. I bought the JL Billet handguard that comes with its own barrel nut. What tools do I need to remove the current barrel nut and do I need some kind of grease for the new nut? What kind of receiver block or clamp/vise?

Might want to check out the Build It Yourself forum.

What barrel nut is currently on the upper? You'll need all of the basic stuff to work on a large frame AR. Based on the fact you are asking some elementary questions, you would be better off taking it to a shop that already has the tools. If you plan on working on these things in the future you could invest in the tools but if you just want to get this gun up and running you would be ahead taking it to someone who already has the tools and experience.

I would agree with what was stated above. That said there are two types of barrel nuts that come with the m5 and you would need to figure out which you have. My buddy had a run of the mill on that took a normal armors wrench but I had one that we found a large crescent wrench worked perfectly. We used a brownells barrel extension torque rod since we could not find a Geiselle reaction rod in stock. We also used aeroshell for the grease on the barrel nut. Basically we took my vise and clamped the tool to hold the barrel nut  and used a torque wrench on the barrel rod to get it where it needed to be.
On this endeavor I think we used the following tools
Vice (run of the mill made in USA one I've had for 10 years)
Brownells torque rod
http://www.brownells.com/gunsmith-tools-supplies/rifle-tools/barrel-tools/308-ar-barrel-extension-torque-tools-prod72374.aspx
Magpul armors wrench or crescent wrench (depends on barrel nut, post a pic and people will tell you)
Aeroshell grease
Craftsmen brand torque wrench
That's everything for just the barrel that we used



His barrel nut
http://aeroprecisionusa.com/m5e1-handguard-barrel-nut.html
Mine
https://pbs.twimg.com/media/Cjd08QmUkAE_kGK?format=jpg&name=large
There may be others as well, the cop platform I got from them awhile back looks like a castle nut!

Thanks. I actually bought the JL Billet handguard. It comes with it's own barrel nut. How can I use that rod with this nut?

OK, what type of upper did you get, the M5, or the M5E1?

The M5 will use a standard AR10 barrel nut, or other barrel nut & rail made for the AR10 platform, whereas the M5E1 uses a proprietary barrel nut and BAR rail mounting system which will not work with any other barrel nut, or any non-BAR rail.

M5...






M5E1...

I have the m5 with standard barrel nut but I bought the JL billet handguard which comes with its own nut.

You will need:
A vise
clamp style vise block or magpul BEV or reaction rod
Armors wrench
1/2" torque wrench
V blocks for the muzzle device
Some type of grease i typically use white lithium since the milspec stuff is like finding unicorn tears
Allen wrenches for the gas block
Rubber mallet, just in case.