Is there an easy way to convert a timeline in FCP to .wmv? I also need to resize the video, from 720p to 600x324 (wmv format) for a client. Is there hope?

Use Flip4Mac.

Dave is entirely correct, but just to address the phraseology of the original question:

You aren't going to 'convert a timeline', or at least I wouldn't describe it that way -- you are going to 'export' a timeline. File>Export>Quicktime Conversion>Windows Media ... if you've installed Flip4Mac your options will include a wmv option that offers resizing, bit rate, et cetera.

Cheers,
GB

I've installed the free version of Flip4Mac and have done that process. I don't see anywhere to resize the video though.

I may be working with a paid version of Flip4Mac, but for me the option for resizing appears in the first dialogue box that appears after I've selected Windows Media in the Export>Format choice, choose 'options' and review the 'video' tab -- the frame size and rate choices are towards the bottom of the dialogue. It defaults to 'current' (same as timeline) and offers many drop-down presets including a 'custom' that lets you make your own choice. The size you are after is a bit odd-ball, but you can make choices and decide whether to preserve aspect ratio, generate an anamorphic file, crop, mask et cetera.

GB