By any standard, your ML needs to be recapped. This is going to be expensive - at least $2K - but the amp shouldn't be used until it is serviced. I'm assuming that it has sentimental value and that you are going to run it in your system for some time. If that is the case then you are going to have to have it recapped. You may as well do it now before you risk any damage. If a board is destroyed the amp is likely to become a boat anchor. If it's like my Krell KSA 300S, replacement boards are rare or not available.
@ imhififan's comment is worth noting. It may not work to hook up a Variac to this amp because it may not trigger the power function with low voltage.
If you don't intend to keep it then I suggest that you sell it as is and don't turn it on. Explain the circumstances in your listing. This is a classic piece of gear and there will be buyers who will gladly take it off your hands in this condition. There are vey few amps available today that can double their power down to 2 ohms and they are extremely expensive. If someone is running vintage Wilsons, Thiels, Apogees, or other speakers with a brutal impedance curve, this amp was designed to drive them.