Where can I find a readable textbook or lecture notes on asymptotic expansions ? 



textbooks on asymptotic expansions 
De Bruijn's "Asymptotic methods in analysis" is an excellent book for beginners. You'll need to work through it diligently to learn everything but no advanced a priori knowledge is required. Also, you can easily download it from many online places that do not worry too much about copyright and, even if you decide to stay law-abiding, it goes for under ten bucks on amazon.


