Hi Jake,
Yeah, your instincts are spot on in this case; that's a classic picture of a broken LCD.
As you've already found, unfortunately iFixit doesn't have any guides for you, but luckily Lenovo provides its Hardware Maintenance manuals to the general public, so good for them. Here's a link to what you need for instructions on how to replace the LCD.
IdeaPad 3 (14″, 05), IdeaPad 3 (15″, 05), IdeaPad 3 (17″, 05) , IdeaPad Slim 3 (14″, 05), IdeaPad Slim 3 (15″, 05), IdeaPad Slim 3 (17″, 05) Hardware Maintenance Manual
Amazon has those screens in stock, but I note there are four different options; you'll need to figure out which one you have so you can get the correct replacement. There's FHD vs. HD, Matte vs. Glossy and one version with a touch screen. The FHD only comes in a matte finish, while the HD screen comes in either matte or glossy, and the one with the touchscreen only comes in the matte finish. With a HD screen, it's your choice whether you want matte or glossy; you can use either one if you don't have a touch screen.
This is just the first result I came up with; it will cost you somewhere between $80 and $90 USD from Amazon. You can also check eBay and AliExpress where you may be able to find it cheaper.
Lenovo IdeaPad 3-15IML05 Screens
crwdns2934105:0crwdne2934105:0
crwdns2934113:0crwdne2934113:0
crwdns2915270:0crwdne2915270:0
crwdns2889612:0crwdne2889612:0
3