Good luck with your toy.
The FLA product is really excellent. Nate is not so good about keeping shipping commitments sometimes. I do hope yours comes soon.
There is a thread on the cncrouterparts cables you should pay attention to if your setup results in a hot motor and/or hot gecko. Basically the motor current set resistor is on the motor side, instead of the gecko side, which Ahren didn't think would be a problem, but it turns out that it is. There are some suggested fixes in the thread, and Ahren has said he will supply a fix to customers who have the problem.
Hopefully you have downloaded the plans and the viewer for them. Get comfortable with the viewer; you will need it to assemble the kit - it's all the documentation you get besides the BOM. There are a couple of helpful videos and pictures on the cncrouterparts website that show how the Z goes together and how to adjust the carriages correctly.
And, there are several of us on the 'zone who have assembled a kit. I have an FLA-300, the 4 x 4 R&P version. It's easy to get some help pronto when you need it.