i got a 305 cfi with AIR and i need someone who has does this kind of a swap before. what do i got to do to make it work? how hard is it to install? and is it worth the gains??

 

Starting at the bottom, it's worth it.

Next, need to establish which headers you're talking about. They basically have 3 different versions:
2055's with A.I.R. fittings, O2 bung, and y-pipe to a 3" slip-fit cat (the best for performance) - the driver's side A.I.R. pipe faces rear (like TPI engines), yours most likely faces front, so you'll have to reroute that hose from the diverter valve.
2052's like 2055's but y-pipe connects to 2-1/2" 4-bolt flange stock cat (better performance than stock manifolds, but a real limitation to performance).
2460's, O2 bung, with or w/o A.I.R., no y-pipe available - have to have one fabricated if you want to use them.

How much else are you doing to the exhaust? The 3" cat and cat back is the best way to go for most performance potential, but you're talking a significant increase in cost.

How much are you doing yourself? You can probably find a shop to do it, expect the labor to cost about the same as the parts or more. If doing it yourself, you need to be able to get the car up in the air on a rack, ramps, or jackstands. The instructions are pretty good. Many people report getting the old system off is harder than getting the new one on. Cutting torch, cut-off wheel, or Saws-all helpful for that.

 

i already got a 3 inch high flow cat and 3 inch flowmaster exhaust
and dual 2 1/2 inch outlets on her, so basically all i need now is new bigger y pipe and the hooker headers without the AIR tubes.
thanxs for the info five!