3.5 hours is quick, Ive had them take 6 depends on the motor and header combo, the 32v stuff can be a little longer.
I personally like the SLP long tube headers and X-pipe, it features removable cats if you need them for emissions testing. Plus they are ceramic coated STAINLESS STEEL so they will not rust on you. Be prepared though, the headers and X-pipe will run you over $1000.
What year is your car? 2v or 4v?