Honestly, it really doesn't make a lot of sense to spend $500+ upgrading a $450 bike, unless you're planning to eventually upgrade the frame, and move all the new parts over...
Depending on your chain, you might be able to use the 32t cog without adding a link...it's hard to say for sure without looking at it. You'd be fine using the 28T without shortening anything.
The new fork would probably be a more noticable difference than the wheels. Get some new kevlar bead tires and you'll lighten the wheels a bit for a lot less...should help until January.
Are you intending to stick with an 8 speed rear cassette?
I really think you'd be better off selling your old bike and spending the money on one you won't need to immediately upgrade- this one, for example.
http://www.jensonusa.com/store/produ...p+Bike+07.aspx