I see many fine horizontal lines across my Chromebook display.

WIthout photos, we have to assume a bit. This is generally going to be a cracked LCD or a TAB failure. THAT SAID: Without a model, we can't locate the screen -- but in lieu of that if you look up your model Chromebook and LCD you can probably locate the LCD relatively quickly. Most Chromebooks do not have expensive LCD replacements as many of them are 11-13" affairs with cheap VA iDP LCDs, which tend to be relatively cheap to replace since many of them use cheap Innolux displays or VA LG LCDs.

That said, depending on the age of the Chromebook and it's EOL status, the cost of a panel may be near the cost of a newer model. A lot of the old Chromebooks only got 3-5 years of updates and deprecaitated off of a cliff, making any repair a "mechanically totaled" issue. The newer 10 year ones hold up better but Google's SW update policies still mean you need to check against how much life it has left before being deemed EOL: Chromebook AUP list

If it's still workable short of a TAB failure and the panel cost vs unit is very close to the same price I'd see about a parts unit with MDM and get the panel that way - assuming the model isn't near EOL.