My thoughts......................
New roof sheathing, 3/8 ply 7 sheets @ $24 $168.00
30' Alpha Systems Superflex Kit @ Ebay complete $469.95
Misc molding for front / rear / gutter / awning rail, misc sealants for same, screws and fasteners, new AC gasket, etc, call it $500.00
May as well replace plumbing vents etc while you're at it, say another $400.00
Looks like about $1500 tops in materials, probably less, if you're handy and have the place to do it. Most likely could be done in a day and taking into account you don't have structural rot as in roof trusses and such.
Even if it takes two guys an 8 hour day call that $1600.00 @ $100 an hour for shats and giggles.
$3000? That sounds a lot better than $7K