1) Well, you just install v176 in itself because 176 is a Major and 3 is the Minor (or as Nexon refers to it, the "PatchLocation"). If the client's handshake doesn't have a valid patch minor anymore, then you can just change the patch version from 3 to 1 and it'd work just fine for your 176.1 client.
2) The redirector you'll use is just a simple MSAuth redirector. I don't think Fraysa's guide was designed for that type of redirection, but I could be wrong as I don't think I've seen the thread?
3) Like it's been stated before though, you don't have to be new to coding. You'll still want to get used to a working and stable build of OdinMS architecture, which is available on versions like 83, not 170. If you have programming and networking knowledge then consider it a plus, if you can learn how to update packets and work with Odin emulators then you'll be just fine working on 170 if you have the time and motivation for the amount of work required to manage it. Your IDE is up to you whether it be Eclipse, Netbeans, etc. Mushy should use Maven (not sure if you're familiar with it or not) and will include a "pom" file that will pretty much handle the big stuff (libraries, etc) and load the source into your IDE for you. So..yes? You just open the project in your IDE with the necessary libraries, update your config, and compile the output JAR. I'm sure this is stated on the Getting Started help on the Git.
4) This is RaGEZONE, which is a massive library for MapleStory. You can find hundreds of sources/repacks for all different versions, languages and regions here. I'd say that it's the combination of preference alongside your goals. What are your plans/what do you want? Most people are ideal with v83, the most common version out there. For v83, you have LocalMS (OdinMS with RMI) and you have MoopleDEV/Solaxia (OdinMS without RMI and updated packets). Others prefer to be v62, which is just closer to OdinMS, but any version of 62 and lower will always include RMI unless you remove it yourself. Assuming you have a networking background, you should know what RMI is or have somewhat an understanding. Once you mess around with a lower version source you can begin learning packets and how to update from version to version. You'll also need to learn IDA unless your goal is to be up-to-date with GMS in which case you'll rely more on packet sniffing. However, once you have the basics down on a lower version and have made sense of everything, then moving to 170+ development will more be your area. Just remember that higher versions lack resources that lower versions have, that's the biggest difference and reason to stay lower version. If you're all about guessing, have real good knowledge of the game and how to packet sniff/work IDA, then being a high version is for you.