That is a very common fear. Not to worry. If you deliver great content upfront and you have already been paid, you should be able to hire out any help you may need.
The point of this “first round” is to prove that you have a product people want. So you wont have to worry about that until you have already been paid.
At that point, you know you have a great product so you can focus on making it great as long as it takes to put out quality. Then all you have to do is repeat the process of webinar or any other method of driving traffic and you will have an asset you can sell over and over again forever.
The only key at this point is figuring out if it will sale or not. One step at a time