This is definitely "renovate". I'll explain the differences here: Decorate - making something look pretty without any physical destruction (i.e. tearing down walls). Putting up pictures, buying some flowers, etc. would be an example of decorating a house. Revamp - this is a bit casual, but it usually implies that you are taking something and making it completely new, or at least changing it significantly. I don't think that I would use it in terms of housing styles/decorations, to me this is more with abstract items - "We need to revamp our marketing campaign so that it appeals to a younger audience". Renovate - this usually implies some sort of physical destruction - new flooring, new walls, new windows, new doors, etc. If you tell someone that you are renovating your apartment/house, they are probably going to think that you are using some heavy tools to do this. If you are just decorating, this is something that you could do over the weekend or on an afternoon. Redo - This is vague and abstract. Let's say you woke up in the morning and did your hair but before you left the house you didn't like it. You could say that you want to "redo" your hair. Your boss may also ask you to "redo" something for them if they didn't like the way you did it the first time (i.e. "Hey, I think your report didn't focus on the right examples. When you redo it, make sure your research is relevant blah blah blah). Another example - suppose you meet someone and are in a bad mood so you aren't too nice to them. Then you meet them again and you realise you weren't too nice, you could say "Hey! I think we got off on the wrong foot. Can we redo?"

Renovating and redecorating would be most apt for what you describe. "Revamp" is ok, but it's more casual, I think. "Redo" is vague.