Let's start slowly and take one thing at a time...the first one being that most of the people that seek help online are the ones who have had difficulties; you're rarely going to find people who had a successful thyroidectomy or thyroid treatment come to a forum like this and talk about how great it turned out. Those people just go on with their lives like nothing happened. So - rest assured that there are many people who have had successful thyroidectomy, get proper treatment afterward and move on.
The biggest problem people have with any thyroid treatment, whether it's post thyroidectomy or not, is finding a doctor that's willing to test and treat them adequately. This means the doctor is willing to test Free T4 and Free T3, which are the actual thyroid hormones, along with TSH "every" time blood work is done. It also means the doctor is willing to prescribe whatever medication is necessary to alleviate symptoms, including T4, only (Synthroid, Levoxyl, Levothyroxine, etc), T3 only (Cytomel, Liothyronine) and desiccated hormones (Armour, NatureThroid, NP, ERFA, etc). Last, but not least, the doctor must be willing to treat so that symptoms are alleviated, not just to get blood work within certain ranges...
That said, I'm assuming you've had a ton of blood work, since you know you have Hashimoto's and, with Hashimoto's, there may be a good chance you have hypothyroidism. Why not start by posting whatever thyroid related blood work you have? This could/should have included, but may not be limited to, TSH, Free T4, Free T3, Thyroid Peroxidase Antibodies (TPOab) and/or Thyroglobulin Antibodies (TgAb). Be sure to include reference ranges, with the lab results, since ranges vary from lab to lab and have to come from your own reports.
What has prompted the need for thyroidectomy? Do you have dominant nodule(s)? Have you had a biopsy that was inconclusive? Please include results/impression of ultrasound and/or biopsy, if available.
Last, but certainly, not least - are you currently on a replacement thyroid hormone medication? If so, which medication(s), what dosage(s) and how long have you been on it/them?