I never read any manuals. If I want to read, I'll read the entire DragonLance series again. If I want to play an interactive, MMORPG, I'll jump right in and have fun. That's what in-game tutorials are for, although I usually skip through them too.
Anyway, level 19 is not too high to start over. Here
http://eqiiforums.station.sony.com/eq2/board/message?board.id=quest&message.id=36250 is a guide to do the betrayal quest, it's not that difficult. Trust me, you may feel like you have invested too much time to just start over, but you may end up level 30 wishing you started over before you put some REAL time in. The general rule of thumb in games like this is that it usually takes an equal amount of time to get from 1 to 20 as it does to get from 20 to 30, then again 30 to 40, and again 40 to 45, and even more time 45 to 50. Don't force yourself to play a class you may not enjoy.
Having said that, if you aren't all that picky as to what you play, I think Ranger is going to be just as fun as Assassin. I'm level 19 too, but I've finished my class quest and just waiting to level up now.