Sally, sorry for the bad news but not to worry too much as it seems to have been caught early. Incisional biopsy (small biopsy) is usually very accurate. T1 stage means that tumor is small but doctor will arrive at final staging only after surgery and histopath reports for the samples removed which will include tumor, margins and nodes from neck dissection.

Has the doctor recommended CT/MRI prior to surgery?

It is not a complicated surgery - glossectomy is surgical removal of part of the tongue along with functional reconstruction, if required and your will have selective neck dissection where they will remove several nodes from neck and suspected structures for histopath analysis. Again, this is a functional neck dissection so it will not affect your head and neck movement though for couple of month you may have pain and may require exercise and/or physiotherapy. Drain tube is important to prevent fluid retention while your wound is healing. You may be in hospital for 3-5 days till nasogastric tube is removed and you are able to eat and swallow from mouth. You may have to go home with a drain pipe as it take few more days to reach minimal drain.

Once you have recovered from surgery and depending on histopath report of the structures removed during surgery, doctors will plan further treatment. In high risk cases, usually chemoradiation is done with weekly Cisplatin and 60 Gy dose of Radiotherapy delivered in 6 weeks.

Take good care of your health and try to regain weight post surgery to be ready, if further treatment is required.