I said this before and I am going to say it again. I do not know if it is worth repairing a 25-year old amplifier. Obviously, you have to get an estimate to repair your current Levinson 331 amp. Are the needed parts available and will the Tech be able to ensure that all the other parts are working correctly to ensure it continues to sound great?
The availability of the original caps are a concern and, if not, what is the impact on the sound quality if other caps are used. Some of the posts above said the Techs are available but are they skilled enough to repair a 25-year old power amp? I do not know.
Your Mark Levinson 331 power amp is 25-years old and maybe it is time to replace it. I suggest you review this repair with the above repair shops and ask for their opinion and the cost to repair including a complete check of the entire amplifier. After this, you should be able to make a decision. please keep us posted. Thanks.