Korean Girl going to korea in February?

anyounghasayoh! hi, my korean name is jindaleh. chin, daleh (flower). i'm wondering if anybody knows a good website that explains the korean alphabet, specifically the complicated vowels, like the difference between ah combined with ee and awh combined with ee. they both sound like eh! also- any really great websites that gives you FREE korean lessons that are accurate and good? i seriously don't want to look like a babo out there in Seoul, SK. so please help!!! any other suggestions to make my travel easier- i'm going 4 a week! last thing- any tips on making my vowels/words/language in general sound more fluent/practiced? thank you all in advanced- gamsahamnidah!