At minimum you are going to need to devote 5-6 weeks away from your job and this is only if you are able to work remotely. If you cannot work remotely then you will have to plan on being away from work for 3 months.
Unfortunately insurances do try to deny coverage for care in order to avoid expense. However, if you have chosen a good medical provider they will fight insurance and provide the support that is needed to state that the curative option of your choosing is needed to your insurance company.