Do I really need a guide for Cho Oyu?
You will need help getting a permit and entering Tibet at a minimum. Once there, It all depends on your skills, money and time available. Cho Oyu is a serious high-altitude climb. Some people go to Cho Oyu without a formal guide and contract with local agencies for yaks, porters or carry everything themselves. There are usually a lot of climbers on Cho Oyu so you would probably not be alone but easily could be. In harsh weather (white-outs) or in a medical emergency, you will be on your own so consider your skill level carefully. Climbing alone or in too small of a team is never a good idea.