Make sure to get a real VGA box, not an S-Video to VGA box (with the real VGA cable the Dreamcast is producing each color separately).
Also make sure that your VGA display is capable of 640x480 (as in a low resolution projector or the old style PC monitor, possibly a 480p early HDTV) Otherwise the quality isn't as good as it could be. But probably better than S-Video (OK, definitely better than s-video, but not the best it could do on a proper 640x480 display).
I don't have any import games, but I think you can burn a CD to play imports at home. I know I have a bunch of homebrew on CDs and it reads them just fine. (no danger in using a CD as a boot disk for imports, it can't hurt the laser.)
Once you make the bootdisk, load the DC with it first, then it will prompt you to swap in your original game. It should load most games, some may not work.
He has quite reasonable price and worldwide shipping. I bought 3 or 4 from him and everything was fine.
640x480p VGA mode is very nice for many games while few of them looks worse. In games like Rez I could easily read all the tiny messages on upper left corner of screen. That was impossible on classic CRT TV.
Here http://dcforums.co.uk/forum/index.php?show...t=0&start=0 you can find VGA compatibility list (maybe you will need to register to see that topic). In short, it's like 95% of games support VGA (some of them only patched for VGA).