How do I repair keys on my advent 5312?

Long story short, I accidentally pulled up one key, to see what it was meant to look like, another and then in anger, another after that. This means I am 3 keys short, and I'm confused as to how I fit the retainer together. Would it be easier to just go to some computer repair shop or would I get charged a lot for something I may be able to do myself? I have the key, it is not broken in any way, it just seems impossible to get it right. And if all fails, new keyboard?