Here is where I got my .300 barrel http://ballisticadvantage.com/shop/b...-blackout.html

Unless you are doing a matching upper/lower or side charger, just about any decent quality upper will be fine. Have you decided on your handguard? Before I would put a Geissele trigger in it, I would look at the ALG (basically the same company) mil spec trigger.

If you don't have the tools, there is a gunsmith in your neck of the woods.