For accommodations, best to look at the TA listings for both hotels, and bed & breakfasts and inns, for each location you intend to visit. You'll find detailed information, and especially informative and helpful the reviews by travellers. My suggestion is to find the lodgings which interest you, and then inquire about prices since the prices published on TA are by the establishments themselves, and often vary greatly based on season, type of room, A/C or not, level of tourism at the time, etc.
In terms of guides / prices, I can only speak for the city of
Oaxaca and touring the central valley sights (ruins, craft villages, churches, ecotourism, etc). You can hop on a tour bus for a couple of hundred pesos each, use a taxi for roughly 120 - 150 pesos an hour, or hire a guide / driver for about $20 - $30 USD per hour.
Earlier today I posted in reply to a question about spending 7 days in Oaxaca in March, and included links to articles about pros and cons of the various touring options, so perhaps take a look at those links.
TIP: Since you suffer from motion sickness, even when flying take dramamine or other similar anti-nausea pills. The flight is breathtaking, but the planes are small.
Alvin Starkman - Casa Machaya Oaxaca Bed & Breakfast
Secrets Huatulco - 
