Figure that you will spend (from Bushmaster) :
$ 36.95 for a Phantom flash hider
$ 106.95 for a Bushmaster 6 position telestock
$100 to have Kurts Kustoms or Randall_Rausch cut that piece of crap off the end of the barrel and permently mount the A2 or Vortex flash hider (including shipping)
And you won't have a bayonet lug.
That comes out to about $993.90 not including shipping for the parts.
You could always buy a new M4 from Bushmaster with a perment Izzy or Vortex for $ 270.00, but then you are still going to be in it for $1126.95, possibly more if you don't know how to R&R an AR15 barrel and you don't have the proper tools.
If you did buy a Bushmaster "preban" barrel you could probably sell your barrel for $120 or so, that will help to bring down the cost of your AR15 to around $1006.95.
If I were you I would just buy one of those NIB Bushmaster M4's for $750 that RenegadeX can get.
Seriously, you should just buy a new Bushmaster M4, they retail at $ 1265.00, but you should be able to get one for about $1000 or so from a cool dealer.
Of course you could always buy a no-name 6 position telestock, I have seen complete ones at the local gunshows for $49, the closed-bottom Phantoms go for about $25, and you could get an Oly M4 profile barrel only for $194.00, that would put you at about $1018.
Then you could always surf the equipment exchange for new or used parts at the smokin deal price.