Hi and welcome to Just Answer!
To get an extension - you should apply for it - and the deadline was yesterday.
It is too late to file for extension.
Now - your only option is to remove excess contribution and corresponding earnings.
However excess contribution (above allowable limit) is subject of additional 6% penalty.
You may ask the IRS to abate penalty if granted - part of the problem will be solved.
For distribution of the excess contribution - you will receive form 1099R.
Because Roth IRA contributions are not deductible - that amount will be distributed tax free - only earnings (if any) will be included on your 2012 tax return - line 15b form 1040 -
You must also pay 10% additional tax on earnings only - line 58.
Let me know if you need any help.