Hello!
I wouldn't say you should study kanji first, although some people do, but you should definitely learn them along with the basics you're going to study.
A lot of textbooks use Hiragana above the kanji, so even if you don't know them yet, you'll be able to read them and slowly remember them.
Learning kanji can be a lot of fun, but if you stop practicing them regularly, then you'll forget them very quickly.
Happened to me, happens to all my Japanese friends, co-workers and students! ^-^; ...