I would like to get in contatct with Admins of large Facebook pages / group who would be willing to post wall updates to their fans/members with our free-to-enter competitions.
debateable - ppl always advertise products / services via status updates - they just dont (unfortunatley) get paid for it. As long as u dont scream "im displaying sponsored ads" you're fine
I can spread the word for your contest .... PM me if interested, and I'll give you links to my communities ....
Best thing to do is leave comments saying "admin willing to pay for updates" and wait for them to contact you.