Did you buy new or used regulators, and an air integrated computer/transmitter? I'm guessing new from your question - do you know any experienced divers who could show you how to do this, and test your regulators?
It would be best if you could have someone show you how to do this in person with you, rather than front up at your class (presumably being run through a dive shop) with equipment you've bought elsewhere that needs assembly - unfortunately you've chosen the best course of action to annoy the crap out of the shop you're diving with - many shops count on post-certification gear sales to students to help stay in business. Showing up to an open water certification class with regulators and computer bought off the internet WILL p*ss them off. That being said, I'm all for saving money where possible.
Get a quote from them before letting them put the gear together, and then get a quote from another shop - be aware that unscrupulous dive shops would use this opportunity to gouge you. This is assembly and testing that any competant diver should be able to do, so if you know an experienced diver, get them how to show you how to do it for free.
The risk you run with attempting this yourself and showing up to OW with untested regs is that something will go wrong - eg the intermediate pressure on the first stage not set correctly, faulty diaphragm in the second stage, a hose not correctly installed leading to an o-ring extruding, etc. The regs need to be assembled, put on a tank of air, and tested for both hose join integrity and cracking pressure to ensure they don't freeflow.
Long-winded answer I know, but try and find someone who can show you how to do this stuff yourself.
While you're at it - fill in your profile details - there may be a ScubaBoarder in your vicinity who could show you this stuff.
Some store owners get weird over people buying from elsewhere.
