I want two people to play minecraft at the same time on my laptop as follows:
(internalMonitor) external-dualhead-Monitor LAPTOP (internal mouse,keyboard) external-mouse-keyboard
I don't care how, but that's what I want. Thanks!
I can not give you step-by-step instructions, but the magic words you're looking for is "multiseat linux" - if you search internet you'll find quite a few tutorials which describe how to configure a system to work in multi-seat mode.
A quick search returned this: Build a Six-Headed, Six-User Linux System
Here's a wiki page from Ubuntu documentation: MultiseatX
The task is not for a beginner user, but it's a great opportunity to learn new stuff :).
Once you have your multi-seat machine set up, you can install Minecraft server and then run two Minecraft clients connecting to that server - that part is easy.
UPDATE: After some reading it looks like the weak link of the whole plan is the fact that you're using a laptop, which implies a single video chip with two outputs. Most articles suggest that configuring two X servers to run on a a single video card is more problematic than running them on separate cards and requires some trickery like using nested X servers etc. Which lead me to thinking that you don't really need two separate X sessions - all you need is to open 2 Minecraft instances and somehow bind a keyboard and a mouse to each of them. So I searched for different keywords and found this question: How to lock one mouse/keyboard pair to each screen? - the accepted answer describes an interesting approach with running 2 separate virtual machines in VMWare (I think VirtualBox may work too) and configuring USB filters for each of the VMs to only accept input from one keyboard and mouse. The OP also states that the solution worked for him. As they state, the soluton does not even require multiple monitors - you can just open multiple VMs and put them side by side on the same screen.