I faced the same dilemma back in Dec. Wait until you can get them together, if you order them separately it will cost you at least another $35 in shipping, not to mention down time on the gun. If you include a credit card number on the order form they jump right to it. I had mine back in less than 3 weeks and that was with the holidays being the middle week. Make sure you ask on the form to take a look at the trigger. They won't do an actual "trigger job" but they cleaned mine up a lot. It went from about 6 lbs pull to 4 lbs, and now it's smooth.
When you ship it out it will fit into one of the medium size postal boxes, just remove the receiver from the stock. You will need a really long screw driver to remove the stock. I just wrapped all the components up in several layers of newspaper and then stuffed the box so nothing moved around.
I'd never ordered a barrel before, so a few observations:
1. Customer service is ok, but not great. Don't expect them to contact you, they won't. If you want to know what's going on pick up the phone.
2. The gun will be filthy when you get it back. Not just test fired dirty but laying around in a machine shop dirty.
3. Signature is required when they ship it back (UPS). I couldn't get a tracking number out them, I missed the delivery and had to pick it up at the UPS hub.