Boss wants me to become lead developer on a huge project; I still consider myself Junior and feel like there is still more for me to learn before I can even accept something like this. The company is amazing and I would love to step into this role but I fear that I will only disappoint.

What would you do? If I should take it; could you recommend resources that would help me level up?

You only grow with things you can't do yet. Uncle Bob told me as I asked him what a senior developer is for him: Senior is someone who takes the responsibility and has or gets the required skills.

I would take the chance. I always learned the most when doing stuff I had no knowledge before.

Agree, senior means you can take full repository.

Senior does not mean you have worked long enough. You will never work long enough.

TAKE THE JOB

My operation manager, who has 50 people under her, joined our company as a junior dev.

Accept the confidence your manager has in you and use detailed planning to guide you along this adventure. If your manager is a programmer then use him as a resource for additional guidance, if he's not a programmer then your best is all he will need; use your existing knowledge to keep him up to date on deadlines and especially any problems that you face. A well informed manager will not be on your case as much as a manager who's kept in the dark. Open honesty with good foresight and options for solutions will help a great deal.

"I still consider myself a junior and feel there's still lot for me to learn"

precisely why you will be good for the position. people who think they know everything they need to know to handle a position are the worst ones to actually handle it, most of the time.

It's your job to do the best you can. It's your boss' job to judge whether your best is going to be enough, and when to put you in that position.

At worst, you will have done the best you can, learned a lot in the process, and your boss will have failed in their job of recognizing when is the right time to put you in that position.

At best, you will have learned that you actually CAN do it, and will have grown.

The jobs that taught me the most, and that I did the best work on, were basically ALWAYS those which I was afraid I'm not skilled&experienced enough to do.

The ones that taught me nothing, which I didn't do my best on, were basically ALWAYS those I was sure I know everything about and can do with no problems.

Fake it 'til you make it.

Every promotion I turned down I ended up regretting.

Every. single. time.

Sink or swim. Up or out.

Fear often is just the compass that points the direction of our desires. Follow it and it will take you to places both terrible and wonderful. But you won't know if you don't go.