depends on the complexity of the dvd, normally it takes me about an hour from the time I finish a project in fcp to the time it comes out as a final dvd that i can put into a dvd player (90% of the time I use dvd studio pro, but for the little projects i can't be bothered and use idvd): Here is the break down:
10 minutes to pick chapter marker locations
10 minutes to export hour long project from FCP
5 minutes to pick the best still frame of the family
10 minutes to put still frame
5 minutes to change fonts in idvd, colors and such
10 minutes to change various preference to match the theme of the video
rest of the time to render and burn.
Although, it can take much much longer if you are working on something complex. I am going to say that the 4 hours is normal.
So i made a OneStepDVD from a file....it was a small mp4 file...after the OneStepDVD was done, i deleted the tiny mp4 file, but now about 4 gigs of space are somehow taken up on my computer...is there any reason for this?
did you bring footage from a dvd, video camera, or other source into the project? That could be worth 4gb, and you can delete that. I believe there is also an option on iDVD (i don't know i don't use it that often) that allows for you to save the created dvd files to your hd, which would also be around 4gb. Did you do any of those things?