This was the project that completed during this break.
The old infrastucture has 1 PDC (2008R2, standalone) and 1 BDC (2012R2, hyperv)
The aim was to replace the PDC with a new hardware due to its age (about 6 years old and out of warranty)
At the end of the project, We have 1 new PDC (2012R2, standalone) and 1 BDC (2012R2, hyperv)

The whole process turned out pretty straightforward and completed smoothly.

As a summary, here are the main steps taken:

1. Install 2012R2 on the new server, Windows updates
2. Add Roles, ADDS 
3. Promote the new server to a Domain Controller
4. Wait for it to replicated across all DCs
5. Transfer FSMO from old server to new server
6. Robocopy, files and folders from old server to new server keeping the same permissions and file structures (because we had file shared from the old server) 
7. Install Files and Storage Services on new server
8. Tested Files/Shares and permissions and are working as expected
9. change old server's name to something else using "netdom computername"
10. change old server's ip to something else
11. change new server's name to old server's name
12. change new server's ip to old server's ip
13. Configure DNS Upstream Forwarder on the new server 
14. Install/Configure DHCP on new server
15. run dcpromo on the old server to demote from the AD, and decommissioned.

Here are some websites that I reference to complete this project:
1. http://jackstromberg.com/2013/10/migrating-domain-controllers-from-server-2008-r2-to-server-2012-r2/
2. https://www.experts-exchange.com/questions/27872748/Replacing-a-Primary-Domain-Controller-with-new-hardware.html
3. https://www.experts-exchange.com/questions/28233238/robocopy-copy-files-from-one-server-to-another.html
4. http://support.microsoft.com/?kbid=125996 (Import/Export file shares)
5. https://technet.microsoft.com/en-us/library/cc835082(v=ws.11).aspx (Rename Domain Controller)

Notes:
Useful commands: (used in this project)
netdom query fsmo, nltest, dcdiag, ntdsutil, etc
robocopy.exe W:\ D:\ *.* /e /copyall /r:3 /w:2 /nfl /ndl /mt /tee /np /log:"C:\robocopy_20170119.log"
Steps to change Domain Controller name:
1. netdom computername /add (add althernative name)
2. netdom computername /makeprimary (restart server after this)
3. netdom computername /remove (remove old name)