I went through this twice (being super small and getting a large enterprise sale), first time was scary, and while I'd love to say second time wan't, honestly it was just as scary but I felt somewhat more prepared.
In my case we had about 100-125 small business accounts on the platform and suddenly had interest from a Fortune 500 firm that had revenue in the 4-5 billion annual revenue and 4000 employees. I had a few more people then just myself (I think 4 FTEs, 1 Part Time), but not enough to support all those users or the needs of an enterprise.
To be fair, enterprise deals can ruin you if you try to approach it like any other sale. They aren't like your SMB sales. Enterprises are wiling to pay because they know their demands are not the same as the local small business. One key thing I learned, you should be honest with the enterprise in saying (something like this), hey we absolutely can support you but as you can imagine it will also mean I need to scale my team to give you the kind of support you deserve and that fits my standards... They love hearing this because it also answers one of their key worries.
There are so many details, learnings, comments, if you are curious and want to hear more of my experiences I am happy to share the good/bad and share. You can find my email in my profile if you want to connect.
Good luck, you are obviously doing something right!