Okay, there's a lot to unpack here.
- If you followed the tutorial and used exactly the image file described in it, you are using a massively outdated version of OpenWrt. 17.01 is, at this point, more than 3 years old and 2 major versions back, and newer versions are much more performant on My Book Live. I would recommend installing the latest 19.07, which you can do like in your tutorial -- or better yet, follow the installation process on https://openwrt.org/toh/wd/mybooklive
- To date, I don't know why you would create and use a swap partition. The MBL comes with a rather generous 256 MB RAM, so unless you want to have really memory-heavy software running on it (Samba not being one of them), you don't need a swap partition.
- If you follow the process on the wiki page, you will have /dev/sda3 and the first thing you should try to do is getting the system to reliably mount it into the same place. This is really not hard to do, I am positive https://openwrt.org/docs/techref/block_mount will help you out.
- Once that is done, we can take a look at Samba. 19.07 does not come with Samba3 anymore, and Samba4 is a huge package, so I would advise to use the new, lean ksmbd (that is, as of now, unfortunately still not very well documented)
Also, don't try to do all of the things at once. One after another, so you will know what step failed. Getting MBL to be a Samba server is not really hard, but it involves about half a dozen things that need to work. And I'm afraid just following an outdated tutorial will not do it, you will have to get at least a little bit involved with Linux.