question about headers

I want to put some headers on my 94 Z28, LT1. Some guy at a muffler shop told me that they would cause problems with blowing gaskets and what not. If anybody has any advice for me that would be cool.
Thanks

??? buy brand name, high quality exhaust gaskets, and you shouldnt have a problem, chances are he just dosnt want to go through the pain in his ass to install headers in an F-body. local shop quoted me 400 bucks to put my headers on my third gen, and 200 more for the catback. needless to say i am setting the car up on ramps to do it in my driveway lol. ill kick myself for it later, but ill use a small ammount of the 600 bucks i saved to buy a six pack of MGD and all will be well again :)

how much horsepower will i gain from headers

id say anywhere from 20-30 would be reasonable. definatly 10-20, but i think 20+ is an easy thing for that engine, especially with those restrictive manifolds it has now. also depends on the pipe size. small diameter tubes are normally known for more torque, less hp, larger pipes will kill some torque but will reward you with lots more power up top. but might i also throw out, that torque i what gets you rolling, i myself am putting on 1.5in primary headers. where most people talk about 1-5/8 as the smallest they go. with 1 3/4 being the norm, and 1-7/8 as the big boys.