How long can a thawed turkey stay in the refridgerator before having to be cooked or frozen?

We bought an 18 lb. turkey for Christmas today, the package said "fresh" & it hadn't been frozen yet. This is my first year doing a Christmas turkey, so I am scared that if I freeze it before then, it won't thaw in time (being I have no clue how thawing times work with turkeys!) The package says "sell OR freeze by December 28, 2008" Will it be okay just leaving it in the refridgerator until Christmas Eve morning? (Which is when we'll start marinating it?) Or do I need to freeze it? I'm not trying to get the whole family sick here LOL! There is a 1-800 number on the package (Honeysuckle Farms) but I sat on hold a lot longer than I had wanted to earlier, & ended up hanging up hoping to get a faster response here. Any help is appreciated! THANKS!