I haven't been able to get FCP X, but if you're gonna use an earlier version, it'd be a good thing to keep a time code log of potential clips from a source you want to use. Mind you, my FCP v.4 does, as stated above, take some time to render vid and audio, which is why I make my vids fast-paced minute-or-less things, then trash the project files afterwards to free up disk space.
To get the screen larger, choose "Scale to Sequence" under "Modify." After exporting, you can make it widescreen with MPEG Streamclip.
And speaking of which, if you want to use some sources that are strike-bait, export using Quicktime Conversion. It may make the image a tiny bit compressed, but it's allowed me to remain under the radar.