Hmmmm...I think that before you do anything else, you should get a couple of books on rebuilding SBC engines. Your questions are not very lucid. Look in the Summit Racing catalogue and there are some good ones, esp. the one by the late John Lingenfelter.
But, in answer to your questions, the bore size has next to nothing to do with the crank shaft. 2nd, inorder for the machine shop to bore your block, they will need the pistons, so you will have to buy those first.
I would suggest that you remove everything from the block, and take the block and the crank to the shop. Ask them to inspect and measure the crank to see if it needs to be cut, or if a polish on the journals will suffice.
Also ask them to measure and inspect the bores. They may need to bore it to the next oversize, in which case they can tell you which size pistons to buy, or they may be able to just clean it up with a hone job....and then tell you which pistons to buy.
Take the rods in too, and ask them to shot peen and magnaflux them, or just buy some new ones.....stock replacementr rods are cheap.....
Also, ask them to remove and replace the cam bearings...
Tim