Just my take on most of the stuff I've had 'proffessionals' do: Trust no one, unless you're right there watching every step of the way.
You will need:
Feeler gauges to check ring end gaps and piston clearance
Ring Expander (I don't like doing this 'by hand')
Ring Compressor to install pistons with rings into cylinders
Rubber tubing to cover connecting rod bolts (so you don't score up the pretty cylinders or nick the pretty crankshaft)
Micrometer/Caliper (a decent one)
Bore gauge is nice, because... Well you just never know...
Torque wrench(s) (3/8" and 1/2" Get the click type. They are cheaper than the digitals, and nicer than the beams)
Plasti-gage kit to check crank/rod bearings
Dial Indicator and magnetic base (nice for checking a number of things)
There's probably a few more that I've forgotten, since I don't rebuild automotive engines anymore. It's more cost effective, IMO; to purchase a Short/Long Block or a Reman. Unless you're building some super exotic, one off, ultra high performance engine....
Personally, I would have the machine shop (if they have a good reputation) assemble the Long block for you. That way, they can do all the measuring/fitting. A reputable shop will check all the critical clearances, even if they've done the machining. Sometimes ya get a bearing, piston, piston ring that aren't right. Rings that are too loose or too tight are just bad news. Same with bearings.
I'm assuming they are also doing the heads? Because if you're assembling them yourself, there are a number of other specialty tools that you should have.
JMO: If you just gotta do it yourself: Have them assemble the short block and heads. Go get the assembled parts and put the engine back together. There's enough 'hands on' just doing that.
"In the end...It's all Hack."