I can only give you my experience, you should be referred to the diabetes clinic for proper support and advice through your pregnancy.
Medication - metformin may very well be sufficient but possibly not in which case you'll be given insulin. Generally speaking, if your fasting result when you first wake up is high then you are more likely to need insulin.
Will it go away - you should be tested about 6 weeks after birth. A HbA1C blood test. Usually GD does resolve with the birth of the placenta but not always. You are also higher risk of getting T2 diabetes later on.
Birth/pregnancy - I was referred to the consultant led route. Had more scans to check for growth which showed DD was big, so I was induced at 37.5 weeks. They do tend to prefer not to let you go overdue because placenta failure is higher risk with GD. I found induction fine, done with a pessary and then they broke my waters after hanging around the hospital for 24 he's. Once my waters were broken Labour kicked in quick and DD was born 4 and a half hours later with the help of a bit of gas n air. We stayed overnight and they tested DDs blood sugar 3 times with a heel prick test, all good and she's never had any health problems.
Diet - low GI is the key term to look for, there are loads of food lists and recipes online. Don't eliminate carbs but switch the junk ones like crisps, chips and white bread for sweet potato, green veg and rye/multi grain bread. If you are having a carb pair it with a protein or fat, so egg on toast, peanut butter on apple slices. Fat is good, ditch all low fat options, low fat yoghurt is chock full of sugar. Pick full fat real Greek yoghurt and add berries. Try not to snack in the evenings, it's good to have a decent period of time when your body isn't having to break down sugar to give it a break. If you do need something make it protein/fat like a chunk of cheese, a bit of chicken etc.
Exercise - really important, a 20 min brisk walk after a meal has a big impact on your sugar levels and building up your muscle through activities like swimming improves your metabolism.
Water - you need to drink plenty of it, being dehydrated affects your sugar levels too.
CGM - may get a free one from diabetes clinic on your first visit but that's not guaranteed and unlikely to be prescribed additional ones. You can apply for a free Libre direct from Abbot www.freestyle.abbott/uk-en/getting-started/sampling.html I am T2 diabetic now 10 yrs after GD, I buy my Libre because I hate finger prick tests but the finger tests are more accurate so it's worth being aware of that.
Symptoms - yes, if you can get your sugar levels more regulated then you will stop peeing so much, although the baby pressing on your bladder may mask that improvement, the diabetes tiredness will improve but the carrying around an extra person tiredness may mask that one too. So can't guarantee you'll notice a huge improvement.
I will say that I found out about the GD when I was about 26 weeks pregnant and the improved diet and exercise meant I ended the pregnancy lighter than I started which as an overweight person was quite a nice side effect.