You drag it into the plugins folder. If you want plugins in your minecraft server use bukkit, not the vanilla minecraft server.
Yes. It doesn't matter if it's LAN I believe. You just have to download some plugins and put it in the plugins server if you're using vanilla minecraft.
Install bukkit
No, Minecraft Realms are 100% vanilla as they are provided by Mojang.
That depends if your minecraft server is vanilla, or with plugins, if it is with plugins like PermissionsEX then yo.u have to add the 'modifyworld' permission to the users permissions
Not GameMaker related
A dedicated Minecraft server is a server where you can play original Minecraft. Usually without plugins or mods.
You can download minecraft plugins from planet minecraft minecraft forums bukkit (for multiplayer) mods for minecraft.com mods for minecraft.net
It is a server that dosn't use mods or plugins
Bukket download it for awesome things
Server plugins only.
There is no way to get married in normal vanilla Minecraft. However, there may be some server plugins that allow you to do this.