Visiting the church of Bom Jesus in Congonhas in an exceptional experience. The various chapels leading to the church contain wonderful sculpture scenes of the Passion by Aleijadinho. Rightfully UNESCO world heritage and not to be missed from any Minas Gereis visit.
We took the taxi from the Congonhas rodoviaria. Getting a taxi back was not straightforward (eventually we convinced the restaurant next door call one). In total we took four hours for the visit (including taxi drives and lunch), which was a bit much. Two hours is however probably too short.
Some information on getting to Congonhas and traveling in Minas. We took the 8am bus from Sao Joao del Rei (Sandra bus company; direction Belo Horizonte), which arrived in Congonhas around 10am. At 2pm, we took a local bus from Congonhas to Ouro Branco (40 min) from where there was a connection at 3pm to Ouro Preto. The bus service is not regular at all but they are very comfortable and drive on time. In short, it is the easiest to get to/from Congonhas from Sao Joao and Belo Horizonte, but the connection to Ouro Preto is quite possible.