Some repair shops have the ability to remove the outer glass, and reuse the lcd. That's why there are cracked assemblies for sale. It's doable, but requires more effort than I care to put into it. On the 920's, I replace the outer glass. For all other models, I do the whole assembly. I have a box full of assemblies with broken outer glass, that I'll sell bulk some day.
If you buy one from ebay, I'd recommend a US seller, because it's easier to return if there is an issue. You'll pay a few bucks more, but it is worth it in terms of service.
Are the $210 numbers for an installed lcd? If so, the extra $30 may be worth it to you. You might need to make sure that includes shipping and insurance, or not, so you understand what the total cost is. Also - for that price, are you getting a new assembly, or just an outer screen? I'd wager the latter.
I had just the outer glass done for a couple of S3's from a guy on ebay, and he did a really good job. It was half the price of online repair places. You have to be careful though, and evaluate feedback carefully. On Galaxies, you can ruin the touch function with the glue process. Honestly don't know on Lumias, because I haven't done that repair.