Help... I'm a lesbian in a man's body!!
I really think Derrick Mason is gonna have a good year, and is gonna be better than Isaac Bruce. If I was you, I'd try to kinda downplay Joe Horn's value and try to negotiate the trade with you giving up Isaac Bruce instead of Derrick Mason. If you can get him to trade you Vick and Horn for Bruce and Green, you'll be incredible.
If it's a no go, I'd probably still take that deal because you have a solid QB in Gannon who doesn't have his bye week until week 8. Vick should be back in week 5 and that gives him some time to recover fully as well. I also have Joe Horn ranked higher than Mason, as the #4 WR in the entire league after Randy Moss... but Mason is 9th and I don't think there will be a ton of difference between the two.