If you're prequalified and prepared to verify all of the information that you've given them, you should be good to go.
Yes you are over thinking this. You need to understand how Lending Club works. They are a peer to peer lender and do not just process the loan doc and send you a check. The pre-approval will tell you what interest rate and loan length and amount you qualify for. It is up to you to create a loan listing and post it on the site. The member lenders then agree to fund your loan request with whatever amount they individually wish to buy. You may end up with only a few or up to a hundred or more individual member lenders buying into your loan.
Although I have not done it with Lending Club I did a loan with Prosper. I believe their time for listing and funding was two weeks. There was little or no activity when the loan was first listed and then in the last few days the remaining 85% of the loan request was bought by individual members and the loan was 100% funded. They also had an option to accept your loan if funding reached at least 80%. Go to the Lending Club site and read the How it Works terms and conditions and you will get a better understanding.
Their pre-approval is all you will get from them. The decision is on you whether you want to accept the terms. I don't know about a hard credit pull with them. Prosper did a soft for evaluation and then a hard pull when I created the listing. I can tell you my experience as a borrower with peer to peer has been a positive one. I have read mixed reviews from the member lenders perspective.