The inhabitants of Andahuaylillas delight in saying their village hosts the "Sistine Chapel of America". Though the comparison is clearly exaggerated, the pretty little Church of Saint Peter the Apostle is lavishly adorned. Paintings, sculptures, ornaments in gold... you won't know which way to look! It is believed the church is full of treasure, which is why the villagers watch it like hawks.
I would advise you to visit the "Museo Ritos Andinos" museum, another village oddity. Its motley collection varies from jewels to mummies to types of corn grown in the Peruvian Andes. Take advantage of the opportunity to try "chicha", native beer made from fermented corn... greatly appreciated by the locals, my taste buds don't tell the same tale!
If you're only on a short trip to Peru, I think it would be better to skip this stop in favour of the major attractions in the Sacred Valley.