Don't even think about re-tuning, bending notes, over blowing or any other stuff like that right now. Just start playing around with your harp. See if you can pick out simple tunes like Mary Had a Little Lamb or Twinkle Twinkle. Keep playing those simple tunes to get really familiar with the layout of your harp and it will be intuitive for you to know where the note is that you want to hear. You have to hear to be able to play the harmonica and have a good ear. You can't see what you are doing like you can with the guitar.
Allenh53, listen to Sarge. There are many songs to play without going to blow 3 and below. Learn the fundamentals first. Bending for playing blues will take so much time to perfect that you’ll probably give up before you discover what you can do. Retuning, like you tune the guitar means scraping a bit off a reed to get it to sound in tune.
As you’ve played guitar for a few years, you probably know how to read music. If so, you’ll know the notes on the staff. Then learn the notes on the harmonica and away you can go, as long as you’ve perfected finding a single hole.
It would be helpful if you told us how far into harmonicas you are. Got any books, know about tongue blocking or pucker etc. what type of music do you want to play. You bring up the subject and someone will post information on it. Stick with it, it gets easier.