I will never have another engine completely built by a shop after what i have found wrong with machine work i have sent out locally. One well known shop just tagged a block as align honed as requested. It was never touched. A set of stock rods came back "resized" and one of the rods had a ding in the rodcap, wouldn't allow it to seat against the rod! This was a well known, trusted shop and i suspect they had a personel problem! So for the cost of the tools to assemble both heads and shortblock, you will be even or maybe save some $$. When I suggest someone do this, along with that goes get a shop manual for the stock motor, (bb right?) ANDYF'S book, and any other well repected books on the motor in question. Take time to learn how to use the measuring tools. Must haves- micrometers, dial bore gauge, valve spring compressor and hieght gauge, dial indicater, to mention some. It takes me a LONG time to screw a motor together, because of all the measuring, checking, double checking i do to make ABSOLUTELY certain i did tighten all those rod bolts correctly, and all the time it can take if you need to FIX something, like when my "lineboared" block cam back and the main caps were off .0005 side to side when i measured the bores for bearing crush.
You will have the support of this web board to help ensure you are doing things right, as well. No question is too dumb to ask either!!