Customize Easy Apache

I hope I am posting this in the right section.

A website we are installing requires the "Multibyte String PHP extension".
After doing some online searches I found where to install this Mbstring on our WHM server, using our Root access.
However, I have never done this before and usually very carefull when installing something or changing some setting of our server, as we have quite a few websites hosted here.

I'll copy some of the steps/messages here:

First of all I go to
Home » Software » EasyApache (Apache Update)
where it show we are using Easy Apache v3.26.9
Then I go to customize our ** DEFAULT ** profile, that uses
Apache 2.2
PHP 5.4
MPM Prefork

Your profile has Apache 2.2.29 chosen to build
Your currently running apache is Apache 2.2.27 (Please note it also gives me the option to use Apache 2.4.10)

In the next step it says:
You currently have PHP 5 installed.
Please choose which PHP version(s) to build
None
5.3.29 END OF LIFE
5.4.34
5.5.18

In the next step I go to Exhaustive Options List where I can choose to install Mbstring.

So far so good, now I have to chose between Save Only (do not build) or "Save and build"
This is how far I've gotten before I got scared ;-)
I'm a little afraid this will change configuration of the server and it might affect other websites we got hosted in this server.

Any advice on this? Are there any risks this affects other websites?
Many thanks!
We use WHM 11.46.0 (build 14) by the way.

 

Many thanks, just did the updated and everything went smoothly