All the legal stuff and the butterflies aside, this would be my approach (for a first time ad integration):
First and foremost, does the product fit what I do and can I stand by it. This company is reaching out to you because you have a voice that people listen to, and they want you to tell the people who listen to you to buy their product. You need to make sure that this aligns with your core values. It needs to be a product that you can support, first and foremost.
After that... have fun! It's your first time, you are totally at liberty to screw it up, be awkward and make fun of yourself, charge whatever you are comfortable with! In the future maybe you need to go nose to the grindstone; get your legal paperwork ready and a bid process prepared. But so long as the company is willing to let you have fun you can do so. If they want a contract that's a little different... but if it is a simple arrangement you can do that once and above all you should enjoy the experience of having been sponsored!
As an aside I will note that ad integrations can be unnerving... I choose to push having fun here because it is a monumental occasion and you should enjoy that. It becomes tedious quick, and the rules and guidelines for ad integrations and sponsorships can get tiresome and make things difficult for you to enjoy the content you are making.
