Southpaw thanks..Wakal i have a stag model 1 carbine. I want like a dpms sweet16 style upper with the 16" heavy barrel and free float tube. I don't want the current factory upper.
ARs are not difficult to work on. The initial cost of a few specific tools is offset as you build more (and you will!). Welcome to the forum! If you're not going to do-it-yourself, check out Dreadnaught Industries LLC Guns Main Page
If you needed some actual machining work done, then I would recommend taking it to a gunsmith, but if you're just putting the gun together-that's not hard. You just need the right tools and there's several publications out there that can talk you through everything you need to know.
Hmm...so you are going from a 16" M4gery (two piece handguards, A frame gas block, A2 flash hider) carry handle upper to a flat top, carbine length free float, single rail gas block, heavy stainless 16" barrel.
You can reuse your bolt carrier group, charging handle, and gas tube. You will need a new flat top upper, carbine length free float tube, rail top gas block, and stainless barrel.
Easier, I suspect, to just buy a new upper (without bolt carrier group and charging handle). No tools needed.
Unless you have a flat top Model 1, then the cost benefit would be on the side of swapping the barrel, handguard, and gas block. About five minutes with the right tools on hand.