Welcome to the fun!!
Old School 3 is a challenge to put together, especially if you go for the 2 different Ludlow backs. I'm a big fan of building sets the old fashioned way, but be warned, you could go through a lot more than 2 more boxes searching for the exact last stickers you need. Think it took until my 8th box to pull the last sticker needed to complete my first set of tan/white/Ludlow, and that was before I decided to separate the Ludlows by back variations and build 2 different sets of those. With the Ludlows, in some instances I had 5 of one variation, and none of the other. So, if you're not that into the sketches, you might be disappointed with the results of $100 on 2 boxes.
Why not post a want list here and see what we come up with? There's a nice size stack of singles in my living room, looking for a good home!