Typically the cabinets are the single most expensive item for most jobs. Appliances and countertops can also add up quickly.
Check reviews, go to website of contractor, ask questions. Ask for references.
Depending on the scope a full kitchen remodel should take 4-6 weeks.
Kitchens have many components and stages to put together. The average cost depends on the scope of work. $25k to $35k is a good estimate.