To what extent was Japan transformed by the influx of ideas and information from China between 500 and 1000 CE ?
It would be hard to overstate the degree to which Japan was affected by China during the time period you mention. Japan's society was transformed in some very important ways. Here are two examples:
First, it was during this time that Buddhism entered Japan. At first, it was limited to the upper classes but, during the 8th and 9th centuries, it spread to all segments of society. It is credited for changing Japanese society in many ways. One example of this is that Japanese started to be cremated more during this time instead of buried. Another is that the eating of animals (though not fish) became much less common.
A second example of the impact of China is the introduction of its writing system. Japan adopted the use of Chinese ideographic and pictographic characters (now known in Japan as kanji) even though they were not really suited for the Japanese language. Writing, of course, transformed Japanese society as it allowed for things like literature and recordkeeping.
These are two of the many ways in which Japanese society was transformed by Chinese ideas in the period you mention.