Irrespective of whether you had a 'contract letter' when you started, you have a contract. It includes the things you were given at the time in writing, anything given to you since, plus a whole lot of implied terms. This means aspects associated with customs and practice of how things are done around the place at present - for example, arrangements for breaks, what you are expected to do when you are sick in terms of ringing in. The very sort of thing that are probably now included formally in the Handbook that the company proposes to give you.
Rest assured, your contract started 3 years ago - so you are not now in a probationery period.
What the company should be doing is giving you an accompanying letter with the Handbook which says something like: Dear XYZ. Please receive your persoanl copy of the Company Handbook, This Handbook now forms part of your terms and conditions of employment as from 1st December 2008. Please indicate your receipt of the copy by signing and returning this letter.