I've always found it easy to substitute foods not replace. I tried originally going vegan by giving up all cheese but that was a huge dietary change that was not sustainable for me. I would definitely say it is now possible to keep one's current diet while replacing the animal products. Vegan meat, milk and cheese have come huge ways. I make this cheese all the time now, I like simple, unpretentious vegan food.

https://shaneandsimple.com/vegan-cheese-sauce/

For supplements, I take Vitamin B12, Iron, and Omega 3. Many people are deficient in these, vegan or not. Things get a lot easier, and after I modified my existing meals it was a really easy change for me. Also I am probably healthier now without all the fat from cheese :P