mob30p to mob30m help (total newb)

hi,

my phone is practically useless with this latest update. the issues are well documented, so i won't go into that. what i would like to do is get my phone back to mob30m, or anything else that will fix the volume issues. google is taking forever to get this fixed.

my problem is, i am a complete novice, when doing these kinds of things. i have been looking around at forum threads to try to get the skinny, but a lot of this is contradictory. my specific aim is to do the following.

unlock bootloader
root
install twrp (or similar)
download the appropriate file to get back to mob30m.
and install that.

i need to know what is the most current (tried) methods of doing these steps.

any help would be greatly appreciated. i'm assuming there might be multiple links i have to look at to get these results, but just perusing these fora is baffling me. :)

thanks