If you can't shell out the money for a Megan Racing header then IMO you shouldn't be buying a header at all. The no-name ebay headers have pretty much a 50/50 chance on fitment, and a 50/50 chance on having crappy welds.
96 Civic DX (an HCF member) has one, but he got lucky and his is alright. However, that doesn't mean you will get lucky.

Also, painted dash parts are pretty ricey and you will probably not like them later on. However, since you're buying new pieces I think it's no big deal, because if you don't like it later on, you can just swap the stock ones back in. Just a warning though, you will probably come to dislike a painted interior.

There are 2 O2 sensor holes because you can use the 2nd one for a wideband O2 sensor to use an A/F gauge. This would be good to have for an N/A build. It comes with a plug, and you just plug up the 2nd O2 sensor bung.