I'm not sure about the level unless it's used to help with the front sight alignment in some way.
Use the barrel vise only if you are installing a screw on hider flashhider or break.If you are using a slip on break or leaving the barrel plain,it's not needed.
Barrel Assembly paste can't hurt.
The Upper Block is the way to go for installing a barrel instead of trying to use vise jaws on the barrel.
A lower reciever vise block is nice but not needed unless you are doing trigger work where you'll be removing parts several times.As for using it to hold the lower while installing the buffer tube,I clamp (using padded jaws)on the thick flat sides behind the mag well to install the tube.You really need to make a set of leather padded jaws for your bench vise anyway.For light work,an old junk mag will do to hold it for minor operations.
Combo barrel wrench:Buy the nicest one with a handle on it and forget the torque wrench.At square hole for a "breaker bar" (pull handle to my hillbilly rear)is nice for one that was over tightened trying to torque it then having to go almost a full hole further for gas tube alignment.
The barrel nut alignment gauge is to align a hole in the barrel nut so the gas tube will slide through without having to use the tube itself for a gauge(this can be made yourself.It's a rod with a taper on the end like a long bullet.If you can find a piece of stock .178"(11/64"plus .007"),you can just grind a taper on the end.Or just take an old 11/64" drill bit,measure the shank to make sure it's not undersize and grind a taper on it.)
The Charging handle looking thing is an insert for the upper to keep from crushing the upper with the blocks in a vise.
One more thing to make or buy is a bench block to support the barrel when installing the front sight base/gas block pins.This can be store bought from Brownells made from several materials (mine's nylon).You can make one out of a pice of wood (oak or maple would be ideal but preferably something other than pine) by making a groove for the base to sit in where it won't roll.If you are removing the pins drill a couple of holes at least twice as large as the pins to recieve them when you drive them out (there's a post about this in this section).
Stupid questions? No,uninformed questions maybe but give yourself a pat on the back for knowing enough to ask before you waste money like I did on the alignment gauge (doh!) or damage something.
Robert.
With apoligies,edited to correct the size of the gas tube alignment tool.I picked up a Rem 1100 slave pin by mistake the first time(double doh!)[smash]
Sorry,Robert.[stick]