Jim, try to find a serial number to post for us. The MM 670 Super was made from 1966-1970. If you have a 1969 or 1970 it may be worth a premium over other models. These were often equipped with a dual pto and console hydraulic setup. A few used the 3 speed TA like in the Oliver tractors. These later models are more desirable for both collectors, and MM farmers.
Its hard to find a good Super 670 for under $2000 in any running condition. Also consider any extras and options it may have. Wheel weights, suitcase weights, canopy umbrella, dual rear wheel hubs... these parts all bring GOOD $$$$...
Motor parts are pretty common for the 336 gasoline motor used in the 670. Don't be shy! Plenty of members on this board can walk you thru the overhaul process, and help find any parts you may require.
Good Luck, Clive