There is no agreement on this issue. You will just have to read all the advice and make the best decision you can make. Some people are adamant prewashers. Others never prewash. Some have never had a bleeding problem. Others seem to have them frequently.
There is also much argument as to products that set dyes. Some swear by them. Some say they are uncessary.
One thing for sure. If the quilt is made to be washed, washing the fabric first won't hurt anything. It may cause you to have to iron a bit more, though.