There's an old wisecrack that goes something like "Don't just do something, stand there." That will probably be their motto. They cannot repeal things done by the present Congress inasmuch as they are unlikely to have a large enough majority to override an Obama veto.
What they can do, in the words of old yachtsman Bill Buckley, is "stand athwart history yelling stop." They can refuse to provide funding for the Obamacare health revisions and other Obama-ish things of which they do not approve. They can send smaller appropriations to be signed or vetoed.