IMHO it's best to render to MPEG2 before going on to the authoring stage. That way you'll only need to do it once - if you leave it to the authoring program you might do it several times as you make changes to the DVD.
I had the same problem. I went out and bought a DVD+R DL (Double Layer )DVD burner from Sony. It cost $250 and it allows you to burn a DVD with 8.5GB instead of 4.7. It will hold your file and it is worth the investment. The disks are a little pricey at $9.99 each but ultimately it is worth every penny.