Gear Lever struggling to shift...

[Caperider]

Everything is on YouTube ! Youtube is my go too when I can't figure something .if you don't find exact fix there is usually something to give you a chance at figuring it out

 

[Racing roadkill]

Everything is on YouTube ! Youtube is my go too when I can't figure something .if you don't find exact fix there is usually something to give you a chance at figuring it out

Unless you have something more akin to the international space station than a bike.

 

[Ajax Bay]

I don't think indexing is needed though is it if they are already in the right positions?

If you only replace the front mech gear cable the rear will of course stay 'indexed'. If the rear is fine I would not replace.
If you choose to replace the outer at the same time, the ease of doing this depends on whether the cable runs along the bar or exits the shifter horizontally. If the former, replacing the outer will require removing (and replacing (?with new)) the bar tape.

The front mech limit screws should not need adjustment (if they're OK at present). But when you replace the cable you'll have to clamp it. Unless you by chance get it 'right first time' some adjustment will be required (indexing applied to the front mech). An in-line barrel adjuster makes this easier, and your double chainset is easier than someone else's triple.
Some good videos around - best one is by the 'well-built' bloke.
I would also be giving the shifter a good dousing with WD40/GT85, sprayed through every orifice and ensure that there's a bit of grease on the cable (only) where it passes under the bottom bracket.