Hi Tyler,
The large building you saw near Sintra is in fact the offices, repair services and sales of the Mercedes Benz subsidiary in Portugal. They did open a classic center. It has an exhibition area and a service and restoration area. However it is a fairly small operation ( the classic part) and only 2 guys are dedicated to classic service and restoration, I visited it about 4 months ago as I was considering taking my newly acquired 230sl which had been standing for 8 years. There were 5 cars being restored and 3 were 113s. Seemed quite professional with good looking repair areas. Prices were just under 50 euros p hour + 23% VAT...just slightly lower than normal /modern Mercedes going rates. Cheap compared to many countries slightly above average for Portugal.
Hope you enjoyed your trip ! Sintra is a lovely place. I live nearby on the coast in Estoril in the Cascais region.
Regards
Pedro