My Mac is dying! Taking longer to start and not loading home screen and menu bar initially. Then menu bar loads but can't open anything for 30 seconds or more. Tried updating IOS X but updates won't load. Any suggestions?

Why don't you try Mountain Lion forums and in using Recovery Mode to restore the system?

I assume you tried repairing your drive and doing a Safe Boot to see if those helps, and you have backup of your system and data already.

Recovery Mode

https://support.apple.com/kb/TS1367

Symptoms

If your Macintosh computer won't turn on, here's how to troubleshoot it. Please keep in mind that although your computer may display similar symptoms that prevent it from showing video, this article discusses what to do if the computer won't turn on, meaning that when you press the power button:

• You don't hear a startup chime.
• You don't hear any fan or drive noise.
• The power button or power indicator doesn't light up at all.

• You may hear a startup chime.
• You may hear fan or drive noise.
• You may see the power button or power indicator light up.

Resolution

If your computer won't turn on, try each of these steps:

1. Make sure that the power cord is plugged into a working wall outlet, and that it's properly connected to the power adapter. (To check if the wall socket is working, plug in a lamp or other electrical device.)
2. Make sure that the power adapter is properly connected to the power port on the side or back of the computer.
3. Disconnect all accessories that are plugged into the computer, such as a printer, hub, or other mobile device.
4. Reset the computer's PMU, SMC, or PRAM. Refer to the instructions for your model:
   
   • Portable (iBook or PowerBook)
   • Mac mini
   • iMac
   • Power Mac
   • Mac Pro
   • MacBook or MacBook Pro
   • Other Mac computers

reset SMC For "Mac wont' turn on or boot" and related

https://support.apple.com/kb/TS1367

General purpose Mac troubleshooting guide: Isolating issues in Mac OS X

Creating a temporary user to isolate user-specific problems: Isolating an issue by using another user account

Identifying resource hogs and other tips: Using Activity Monitor to read System Memory and determine how much RAM is being used

Starting the computer in "safe mode": Mac OS X: What is Safe Boot, Safe Mode?

To identify potential hardware problems: Apple Hardware Test

General Mac maintenance: Tips to keep your Mac in top form

First, back up all data immediately, as your boot drive might be failing.

Take these steps when you notice the problem.

Step 1

Launch the Activity Monitor application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Activity Monitor in the icon grid.

Select the CPU tab of the Activity Monitor window.

Select All Processes from the menu in the toolbar, if not already selected.

Click the heading of the % CPU column in the process table to sort the entries by CPU usage. You may have to click it twice to get the highest value at the top. What is it, and what is the process? Also post the values for % User, % System, and % Idle at the bottom of the window.

Select the System Memory tab. What values are shown in the bottom part of the window for Page outs and Swap used?

Next, select the Disk Activity tab. Post the approximate values shown for Reads in/sec and Writes out/sec (not Reads in and Writes out.)

Step 2

You must be logged in as an administrator to carry out this step.

Launch the Console application in the same way as above. Make sure the title of the Console window is All Messages. If it isn't, select All Messages from the SYSTEM LOG QUERIES menu on the left.

Post the 50 or so most recent messages in the log — the text, please, not a screenshot.

When posting a log extract, be selective. Don't post more than is requested.

Please do not indiscriminately dump thousands of lines from the log into a message.

Important: Some personal information, such as your name, may appear in the log. Edit it out before posting.