If you can only take museums in small dosages, save your energies for the Museu de Arte Sacra in Mariana, well worth a visit.
The Incredible Aleijadinho
It's impossible to go anywhere in Ouro Preto (or any of the other historic cities, for that matter) and not hear the name or see the work of Aleijadinho. Brazil's finest baroque artist, he carved much of the soapstone decorating many of the finest churches both in Ouro Preto and in the other historical cities. (The church of São Francisco de Assis has some particularly fine examples of his work.) His signal achievements are all the more remarkable given that Aleijadinho worked without the use of his hands. The son of a Portuguese architect and a black slave woman, Antonio Francisco Lisboa was born in 1738, inheriting the name Aleijadinho in his 20s when a debilitating disease -- probably leprosy -- left his hands and legs crippled. Undaunted, Aleijadinho carried on working, even as his body degenerated to the point where his apprentices had to strap hammer and chisel to his wrists. He died in 1814, having completed his last sculpture just 2 years previously.
Choose Your Guide Wisely
The square in front of the São Francisco de Assis church is particularly notorious for the guides that try to sell their services to visitors entering the church. Some are incredibly knowledgeable and will greatly add to your experience; others are trained only in spewing completely useless facts and can't answer any questions. If interested in a guide, check with the tourist information office on the Praça Tiradentes, or when negotiating with a freelancer be clear on the amount and the length of time (will he/she just give information on one church or visit a number of monuments with you?).
This quote was taken from one of the English-language guides for sale in Ouro Preto: "The constructive process of the temple began in 1733, reaching the decade of 80, when the frontispiece was concluded with base in Manoel Francisco's risk." In short, buyer beware!
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.