Made the mistake of shooting my shots with 1920x1080 30. I shot some with 1280x720 60 for slow motion. I know I have to reduce the speed to get the slow motion, but is that going to screw up my timeline on FCP if the rest of the video is in 1920x1080 30? Help please, asap. Thank you!

Most likely all you will have to do is scale the 720 material if FCP doesn't do it automatically for you when you put it on the 1080 timeline. Probably also need to render the material for best playback.

if this is as basic as i think it is, the answer lies in conforming to 30fps. do a google search, pretty easy to do in cinema tools.

I work in Adobe Premiere, not FCP, so take this for what it is worth:

There are two frame rates you need to think about, the frame rate you're filming in and the frame rate you're playing the footage back at (in our case as video editors this usually means the frame rate of the project or sequence or timeline in our editing package).

I usually edit my projects on a 24p timeline, so it goes like this:

24p footage when played back at 24fps on the 24p timeline = normal speed
30p footage when played back at 24fps on the 24p timeline = ever so slightly slower speed
60p footage when played back at 24fps on the 24p timeline = very slow--more than half speed