There's nothing scary about that, as long as you keep track of what you're doing and not pushing the wrong buttons. Are you sure your provider even offers LTE? Also, I don't think the
4636 works on that model. You probably need to navigate through the Service Menus with
*#0011# and then hit (menu)
Back and then (menu)
Key Input and enter
Q0000 and wait...
Now, depending on where you bought you phone (EU, US etc), you'll have full access to hundreds of ways to mess up your phone settings and even brick your phone. So I can't tell you how to find the LTE specific menu. But there are several LTE related items in the CDMA sub-menus.
For a more technical hack for enabling LTE bands, please see the following two XDA posts (and threads) here and here. Please note that this involves using Qualcomm QPST and QXDM diagnostics tools.
You need to be rooted. The easiest way to do this, is by these 2 steps:
1) from a root command line (shell).
# setprop persist.radio.lteon true
2) Then go to the Samsung Service Mode menu, by dialing the shortcut
*#2263# (BAND). There you select LTE Band Preference and then LTE ALL. (To undo, either select "Automatic" or "WCDMA Band Preferences" -> "WCDMA ALL".) Finally reboot your phone.
If these doesn't work you may also try dialing