Hi Dolly,
Your 153 has 2 circuit boards. The one in the back is the L-print, and the one in the front is the S-print. Both are available and very easy for your Bernina dealer to get. The S-print has a retail price of $306, and the L-print retails for $298.
So, if you were to find a good, used B153, you'd probably pay about $500 -- $600. Then it might have a bad circuit board, and you'd be back to square one.
Another thing to consider, is that all of your presser feet WILL work on any newer Bernina. They are the "new" style feet. You might be better off getting a new Bernina 330 for around $1000. They are mostly the same machine on the inside as your B153.