Just diagnosed

Graves is hyperthyroidism. Your body is in hyperdrive thanks to it. Your thyroid is probably growing too large and they need to take out part of it to prevent damage to your body. It can harm your heart and cause muscle wasting.

Hypothyroidism is a slowing down of the system.

I suggest you buying a book on the subject to research more. I like the book "Thyroid for Dummies".

I did some resaerch for you:
Thyroid peroxidase antibodies are seen in nearly all patients with Hashimoto’s thyroiditis and 70 percent of patients with Graves’ disease. Recent studies show that unlike thyroglobulin antibodies, TPO antibodies are indicators of thyroid inflammation.

Thyroid stimulating immunoglobulins, also known as TSIs, are autoantibodies that are produced by the immune system in the setting of Graves' disease. Antibodies are molecules produced by white blood cells called B cells. B cells are stimulated to produce antibodies through a series of interactions with other white blood cells called helper T cells. These interactions transform B cells into plasma cells that secrete large amounts of antibodies.

In other words the tests are saying you have Graves' disease and your body is trying to fight it.
It will be okay. It is very easy to manage. There's no cure, but medication and the possible surgery will help you feel better.
They probably just want a biopsy to check it for nodules and such. No biggie. :)

The most common cause of swollen lymph nodes is an infection, particularly a viral infection, such as the common cold. However, there are other types of infection, including parasitic and bacterial, and other possible swollen lymph node causes. They include:

Common infections
Strep throat, Mumps, Measles, Ear infections, Infected (abscessed) tooth, Mononucleosis, Wound infections
Tuberculosis, Certain sexually transmitted diseases, such as syphilis, Toxoplasmosis — a parasitic infection resulting from contact with the feces of an infected cat or eating undercooked meat, Cat scratch fever — a bacterial infection from a cat scratch or bite
Immune system disorders, Lupus — a chronic inflammatory disease that can target your joints, skin, kidneys, blood cells, heart and lungs, Rheumatoid arthritis — a chronic inflammatory disease that targets the tissue that lines your joints (synovium), Human immunodeficiency virus (HIV) — the virus that causes AIDS

Cancers

■Lymphoma — cancer that originates in your lymphatic system
■Leukemia — cancer of your body's blood-forming tissue, including your bone marrow and lymphatic system
■Other cancers that have spread (metastasized ) to lymph nodes
Other possible, but rare causes, include certain medications, such as phenytoin
(Dilantin), used to prevent seizures, and certain immunizations, such as for malaria.

Ouch! I hope they do both tests while you're under sedation. The bone marrow test is painful according to my mother who just had it done. She has what used to be called pre-lukemia.

Low TSH is hyperthyroidism. Graves is a type of hyperthyroidism.

Get you a book on thyroid information. It will help a great deal.
I liked "Thyroid for Dummies" it was very informative and answered many questions for me.