"A bit" is quite an understatement. Migrating a cocos2d v2.2 project to cocos2d v3.2 is a huge job (the larger your project, the bigger the job), but it's doable. (I'm talking from personal experience.)
Changing CCLayers to CCNodes isn't really the biggest issue. Changing all your buttons to the new CCButton is much larger (note that CCMenu is also gone, and now buttons are independent of everything else). Also if you use shaders, that's another one (possibly even larger). If you use the 'color' and 'opacity' property of CCNodes, that's a big change too (pro tip: It helps if you make your own CCNode interface extension that has for example a color3B property that works like the old .color property.)
Also, the new way of implementing the app delegate is completely different from v2, so you should check that out (or else your program won't even run).
Mind you, most of the changes are for the better (even though personally I find the new color management to be too complicated for the hypothetical benefit it might give; personally I use a custom CCNode extension to make specifying color and opacity like in v2. So far I have noticed no drawbacks.)
If you have any code that uses texture uv-coordinates directly (eg. in shaders), you'll notice that for some reason textures are now inverted vertically, so you'll have to fix all your uv handling for that.
Also, if you have any code that creates custom meshes or does other kind of custom rendering, the approach is also completely different in v3 than in v2.
Also, CCNode's tag property is gone. (You might want to add it to your custom extension of it.)