I am currently paying a Photoshop whizz to edit product photos for me (e.g, a lampshade), replacing the pattern with other patterns and colours, to use on my nursery décor website. I wondered if there was a free and easy way to do this myself, bearing in mind I have zero photo editing experience?
I'm not going to answer with a "how to". There are tutorials online for this kind of thing, and other answers here on GDSE that would help. However I would like to answer more generally on the question of whether you should do it yourself, or hire someone with the relevant skills.
GIMP has a steep learning curve like Photoshop, but it is capable of many of the things Photoshop can do. However, it's not easier, and in fact arguably it has less automation, and requires more manual effort than Photoshop.
The thing you need to ask yourself is if you have the time to devote to learning how to use the software. Or is your time better spent elsewhere, and your money better spent getting someone with the right skills. After all, time is as much a cost as money spent.
I'm not trying to put you off trying, or attempting to learn. I just want to let you know that GIMP is not an "easy" option. As for tutorials, youtube is a great resource for these.
@RiannaBateman, often it's simpler, faster and more easily reproducible, if it's feasible, to have a simple 3D model of the item in question, working in some program like Blender or modo, and then switch out the material of the given part being graphically versioned, and re-render.
Just a thought.