Random thoughts: Miraflores is a nice area of Lima, some good restaurants and some nice "pensiones" (sort of a cross between a bed and breakfast and a motel - all the ones I've stayed in have been very nice - google Miraflores and Pension, I'm sure you will find some). Arequipa "the white city" is lovely, and has an inactive volcano near it called "Misty". The Nazca lines are great from the air, but almost invisible from the ground. There are some old burial grounds around Nazca. If you can get to Lake Titicaca (the Peruvians say the "titi" part of the lake is in Peru, and the "caca" (poop) part is in Bolivia - I think the Bolivians do it the other way around) and have the time, take the train from Puno to Cuzco, and see Machu Pichu. The train trip through the the Andes is comfortable, and the scenery and villages along the way are great.
I don't think you'll need a guide unless you want to get a ways off the beaten track. I'd just hire a taxi recommended by wherever you're staying. If you don't speak Spanish get someone to tell the driver what you want to do, or ask for one with some English. Negotiate the price before leaving. Get a travel dictionary. Try a Pisco Sour and the paella.
I'm jealous. Have a great trip.