If only we could write to Japanese-speaking Bloo...
Well, I know some rudimentary Japanese, so I looked over at the Wikipedia page for this movie (first, went to the "X from outer space" English page, then clicked on the "nihongo (japanese)" Link under Languages on the left sidebar)
The name Guilala itself is in the movie title, but in the phonetic "katakana" alphabet: Gi-ra-ra, and no matching Kanji anywhere else in the page that I could notice... and the rest of the movie title roughly translates as "Gigantic Space Monstrous Beast Guilala." That's all I can help with.