Will bitcoin core have to re-sync the whole block chain if I replace my wallet? I have an old wallet from 2013. After backing up and replacing my current wallet with the new one, will it require the client to re-sync and re-download the whole blockchain? Last time it took about a week so I'd like to avoid it.
No, it will not need to redownload the entire blockchain. It may need to rescan the blockchain, but that does not require downloading any of it and will not take as long.