Hello and welcome,
What you are feeling and thinking is absolutely normal following a shock diagnosis of diabetes. Most of us have been there in your place, but rest assured you will feel much better about it if you take a deep breath, make a cup of tea, and read round these forums. We are all diabetics of one sort or another, so who better to listen to and take advice from than us?
It is absolutely NOT impossible to return your glucose levels to normal, despite what your doctor says. He is wrong. Many, many members on here have brought their glucose levels down to normal and come off or reduce medication. Many members had higher (much higher) levels than you when they started, so please do not despair.
Yes, you will be monitored regularly (every 3 months initially) and this includes blood tests not just for glucose but also cholesterol and lipids, liver & kidney functions, full blood counts, and urine tests. You also receive an annual retinal eye screening test and annual foot checks, which are both hugely important for us. This is also not forgetting the usual blood pressure checks.
Providing you find an eating plan that is suitable for reducing blood glucose, and also sustainable for you in the long term, you should see an improvement quite quickly. In order to help you with this, you will need your own blood glucose meter, otherwise you are working blind. I have little doubt that your doctor and nurse will tell you not to test, but this is a financial decision, not a sensible one.
I won't bombard you with stuff for now, but will tag
@daisy1 for her very helpful introduction post. Meanwhile, read this forum, and ask as many questions as you like.
PS. If you are worried about cholesterol, make sure you have the full breakdown of the levels - HDL/LDL/triglycerides. A print out of your blood results will give you this information.