I installed a complete bellanger system from the headers back on my 98'GTS and it was fairly simple. I used the copper tube for the flanges back. I found that the stock manifold gaskets worked best (Metal) they cost me $35 from D/C. The hardest part of the install was removing the old system. Alot of the band clamps rusted together, so make sure you buy a bottle of rust penetrant. Also after you put your new headers in, if you choose to leave the heat shields off make sure you protect the pressure bottle hose on the bottom of the tank. Unfortunantley I found that out the hard way, but I also learned how to flush my radiator because of it. LOL
Good luck
P.S.- PM me if you have any other questions