All of these questions should really be addressed to your domain registrar.
1. How can I get hold of the new registrator (My contact information
still appears in the whois databases)?
If that's true, then it would appear that your domain name was not actually fully expired. When a domain is expired the old whois information should be purged, and then when it's re-registered by someone else the new details should then be present.
Without knowing at least which TLD it's in (and maybe the whole name) it's hard to guess more.
It's possible that the domain registry has themselves pointed your NS records at their own link farming pages.
2. Is it possible to appeal to any authority to claim ownership?
Talk to your registrar, and if necessary the TLD domain registry. What they do will depend on the TLD's policies though.
3. Is it possible to contact google about removing the page from the search engines?
No, as far as I know Google will not arbitrate in cases like this - as far as they're concerned the new content is legitimate and there's no reason not to index it.