Hi guys. I bought a 2010 Trek FX 7.3 from Craigslist. All of the brake and shifting cables/wires have rust on them, so I want to replace them. I think replacing the brake cables will be easy, but I'm worried about replacing the shifting cables.

It looks like the cable is attached inside of the shifters. I'm a complete bike rookie, so I'm afraid that if I open it up, it may be complex, and I might not be able to put it together again. So is there any way to replace a shifting cable without opening up the shifter? And if not, how would I go about opening and replacing the cable? My shifter is the Shimano EF60, 8-speed trigger.

I know this should probably be on the Mechanics section, and I will probably post it there to, but I wanted to try this forum, since it's a road bike and you guys know a lot about them. Thanks.