Welcome gidxg03,
We need scripts for two main reasons: resize (tmpgenc resizer is not as good as avisynth) choosing automatically the correct aspect ratio and remove DCT blocks.
DCT blocks are those annoying dancing blocks that appear in dark, flat areas.
Yes you can convert without scripts. But you'll have to resize to the correct aspect ratio by hand, and you'll not get the best quality possible.
But keep in mind that using scripts is easy. Writing then is a little bit harder. You just have to install avisynth, create in notepad a file named "mymovie.avs" or something like that, paste inside the commands I suggest, and change the first lines to reflect your movie name with path, target width and so on. If you run in trouble, you can always post your edited script here and we'll try to help. But since you're dealing with DivX, you should post on the DivX forum.
Of course you have to change the bitrate. You have to use a manual prediction method I describe in the guide to achive the right size to fit.
[]'s
VMesquita