i had no name exhaust part, muffler plus some other parts installed 3 years ago, its making noise again, and it also
sound like something comming from nearer to the engine...
Assuming I need everything from the engine to the muffler, Is the dealership installed parts worth the extra cost ??
Not necessarily better than aftermarket - really depends on the quality of the aftermarket part. In general though - OEM generally will hold up better than most aftermarket parts. Granted, you will pay more for OEM - but since it is bolt on and go - you'll know that fitment is 100% correct.
A good exhaust shop should be able to fabricate an aftermarket exhaust system that is every bit as good as the OEM one. I've had them replace the one on my truck (OEM was stainless - but was showing lots of surface rust and galvanic corrosion from the mismatched metals) - with a mandrel bent, thick walled, aluminized mild steel one - almost 10 years later, that exhaust still solid.
Before you commit to a new exhaust system - might be worthwhile to inspect what is wrong with the aftermarket one you have. Gasket got blown out, crack in welds, loose clamp, corrosion perforated through piping, etc. Especially if this is what killed the original exhaust - might work on something that could beef up that weak point.