Hi daszoeb Yep you sure can in Vision. Add the files then highlight both. At the bottom left hand side of the content window is 3 buttons - the middle one is merge. Click that on to join the files.
What kind of version of Nero do you have - is it an oem version that came with a burner or did you buy Nero? If it's an oem you may not have Nero Vision Express. But here's some links for version 6.6.0.18 Package 1 Burning Rom, Express etc. Package 2 Recode, Vision Express etc.
Yes that what Vision does - will convert to dvd complaint video that will play on your standalone. What did you use to combine them? You may not have Vision with the oem version.