Rebecca, No, it will not read 1 gig HiMD discs. It was made prior to 2004, which is when HiMD came on the scene. It does do a very good job at recording standard MDs, however.
I have a mint condition MDS-JB930 Minidisc deck for sale. I've had it about 4 1/2 years and have only used it maybe a dozen times. It works great and has no known problems. You can read a list of features and reviews here MD Community Page: Sony MDS-JB930 . This is a well respected component...