Alright soo first thing is that probably none of that will help in range or accuracy other than the barrel.
second - this one would be much better! but if you prefere the shorter barrel its a personal preference :
http://www.airsoftparts.ca/store2/in...oducts_id=1854
Third - that nozzle set may help reliability and longvity because WE parts are not the best made from what ive heard. I am biased as i ONLY have TM. But it couldn't hurt to put it on? Be warned that the oring on the piston head is touchy. If it swells it can get jammed inside the nozzle and cause alot of problems. Additionally, the floating vale may also not be necessary since it could cause more problems due to the strength of your 'stock' floating valve springs and it may cause problems down the line.
The recoil spring is alright though as WE's seem to have lazy recoil. The hammer spring is not always necessary but couldn't hurt to install.
is this 4? or 5? -- the guide rod plug - will not help with anything. It is all aesthetics.
6- MOST IMPORTANT! DO NOT!! buy that guide rod and expect it to work with THAT specific guide rod plug. You need to have a guide rod plug that is open ended to allow the extended guide rod to come through it.
That being said. The guide rod probably wont do much for you. If it makes you feel better personally having it installed then you can go for it. It may help keep your slide straight and less wobbly. But remember you need an OPEN guide rod plug to let the rod through!
7- Im not sure what hop rubbers are compatible with the WE, but you can always look into a better hop rubber to go along with an inner barrel. There are many TM compatible ones but i dont have the experience to tell you if they fit a WE.
Best of luck