The Banks, you have the idea. Although it's not "true dual" all the way back, it gives that appearance. Yes, you would need a 1 in and 2 out muffler. Some of the systems need welding, from what I've seen most use clamps, either traditional exhaust clamps, or the more expensive ones tend to use band clamps(probably for astetic reasons). As far as labor, it's going to depend on the shop. The muffler does not affect your emissions at all, it's simply for noise regulation, so smog won't be a problem. Theoretically it could have some performance gains by allowing more area for the exhaust to flow through, but the difference between a single tip and a double tip won't make too much difference if you have the same type of muffler on each and the only difference is how many outputs it has.