It's not hard to replace carb. Weber gives all the directions and we also have manuals here you can download on an install also. The Weber kits come with all the hardware and gaskets, you will have to do a little thought on the linkage connection but it hardly can be called difficult. You should be able to replace a carb in a few hours and have it running and mixture set. It's one of the best increases in horsepower and I think I even get better fuel mileage with my Weber. You will have to block off your EGR valve stuff probably since it will not be really used, but Weber gives all the info on what is to be done. We can help also if you have any problems since over half the members probably run them or have. The carbs run from about $250 to $300 and you'll never have to deal with the old Mikuni again. You can probably clean it up and sell it on Craig's list or EBay and make some money back to help pay for the new carb. If you do buy a Weber, Redline is a good place and EBay, but look around to find a good price. Most of all be sure you get the real weber and not these fakey Webers that people find on the web.

If you have to have your vehicle smog certified, you may check what your allowed to do by way of changes in your state. My vehicle is exempt from smog test now because of it's manufacture date.
I'm not trying to push a carb on you, make your own choice if you find out your carb is bad and it will cost more to fix then getting another carb.