Removing the glass can be difficult. You have to be careful not to damage the LCD Panel, the wireless antennas, camera & camera cables. The glass is held on by very strong adhesive (Apple loves adhesive). You will most likely end up cracking the glass more than it already is with glass shards flying at you. Definitely wear safety glasses. While the glass can be removed while the Display is attached to the laptop, I find it easier to first remove the Display.
Chances are the glass you receive may be pulled from another display. It may or may not come with adhesive pre-installed. Even if it has adhesive, it may not be very good. If the glass arrives without a piece of plastic covering the inside portion, then getting it clean enough is difficult due to the one chance you have with the adhesive. Even with a plastic cover on the inside, the glass may still have blemishes needing to be cleaned and there is always dust. You cannot tell if there is dust or a smear until it is sitting on the Display with the dark LCD behind it. If the pre-installed adhesive is not good, then removing it is a pain and you will need to apply your own adhesive tape.
The vendors I mentioned in the earlier post may sell the glass as well, but may not always have stock. You may be better off buying a complete Display Assembly. The same vendors may sell the Display as well. Check their used Display prices. They have several categories for used parts so you may find a used Display with slight dents or scratches that may be acceptable.
I'm sure there are a lot of other reputable vendors out their selling parts and refurbished laptops.
Once Apple stops supporting the OS for this laptop, then Safari will no longer be updated. Once Safari stops getting updates, you will find some websites that may stop working correctly plus you will be more vulnerable because Safari is not getting security updates. It may take a little while, but it will happen.
Third party browsers are Firefox, Google Chrome, and Vivaldi among others. These browsers may continue to be supported for a while, but it is only a matter of time before they too will stop being updated. Third party browsers (and app developers in general) try their best to support systems as long as possible, but sometimes Apple makes changes on newer systems that force the third party browsers & apps to drop support for older systems.
It is really hard to judge how much time you have before this happens. My guess is two maybe three years tops if you are running OSX 10.11. But this is just a guess and I could be wrong. Your laptop is 10 years old.
When this happens, there is an option to install a non-Apple OS such as Ubuntu or Linux Mint on this laptop which should run quite well with 4GB of RAM, but it is not for everyone. Both include multiple graphical user interfaces which can be overwhelming to new users (KDE and LXDE are my personal favorites with Mate coming in third). It requires learning a new OS. You also won't be able to use many of the familiar proprietary apps, but it will keep you online. And it is free.
According to this site, this laptop may be able to unofficially support 8GB of RAM (2x4GB) if it has Boot ROM version MB51.007D.B03. Double-check that I selected the correct laptop there.
Good luck.
