From expirience a botched sysprep is really bad and a reimage with a clean image would be ideal, but I know you said that wasn't an option. If after the repair the machine isn't working I'd honestly just go with a rebuild. While I don't know your exact situtation you will likely spend more time trying to track down the problems then you would with just biting the bullet and sitting down to reinstall.
That being said dll files aren't all that hard to get and place if you know which one you are looking for. You can take a dll from a working computer or from the internet.