You will have a great time. It will cost about US$100 US to fly from Lima to Cusco, which is the nearest big airport to M.P., and about US$70 to take the train to M.P. However, Cusco and its surrounding areas (the "Sacred Valley") have as many or more "sacred sights" (e.g. The Coricancha")as M.P. so you'll want to spend at least four days in and around Cusco, including overnight in M.P. (or Aguas Calientes close to there), which I'd recommend To Lake Titicaca, take the train from Cusco, which is somewhat expensive--around $250.00 one way, then take the bus or train back to Lima via Arequipa. You can also fly to Juliaca from Lima. Buy your ticket to M.P. in Cusco because you can no longer get it at the gate.

Lodging and meals in Peru are very reasonable, and you can get a very comfortable hotel room in Cusco and other places that are not Lima or M.P. for around US$25.00, although probably more expensive near M.P.

As to the other sacred sites--on the north coast, Trujillo and Chiclayo have lots of pre-Inka temples and so-forth--The "Lord of Sipan" museum (Museo Tumbas Reales de Sipán) and archaelogical sites outside Chiclayo are some of the best. In the mountains, take a bus from Lima to Huaraz and then a tour to Chavin, one of the best archaelogical sites--very important early site. Buses from Lima are quite reasonable.

Nazca Lines outside Nazca, south of Lima on the coast are also worth seeing, although you have to go in a small plane, which is quite pricey.

Of course are lots of churches, monasteries, etc., if you're interested in Christian sacred sites.

I recommend making all your in-country travel arrangements once you get there, because you can get them for much less than on the internet.