Replace Manifold or Go Headers?

Wondering which way to go, replace manifold or start over with Headers, Have the motor out of truck for repairs right now and looking for suggestions. Will likely be doing the work myself so emmissions won't be an issue. The original o2 sensor was found dangling by the wires for who knows how long and I havent noticed any difference in performance.
Do I really need to worry about getting one back in? And how would I do that if I go to headers. Is there a good sorce for headers on the web? How much should I be looking at for a decent set?
Never really been a performance nut so these may sound like stupid questions but I figure better stupid questions than stupid mistakes! Any suggestions will be greatly appreciated. My goal is not to gain a bunch, just get everything back together and have a decent setup that was worth my time
Thanks
Rich





