Re the doors, don't worry - it's pretty easy.
The fiddly bits are getting the cover off from around the locking knob in the top corner. You may break the retaining clip for it if you're not careful, though it will still function without. Likewise, count on breaking at least half of the trim clips - just replace them. It's worth buying the proper
trim removal tool though, as it does make the job easier.
Then, before you take the window handle off, note its position with the window fully up, so you can put it back at angle angle that won't attack your calves.
The lock barrel replacement is pretty straightforward. Whilst you're in there, it's worth checking for rusty bits around the bottom of the doors and painting / treating them, and also greasing up the window winder mechanism for good measure.
Hope that helps!