Please Help me get my truck fixed

Hello, 

Recently my main source of transportation developed two badly leaking freeze plugs.  One on each side of the engine.   I literally am completely strapped financially.  I am on permanent disability and fighting to get my VA disability rating.  I am on a very limited income, and out of my paltry $1200 per month that I get from SSI I have to pay over half of that out for just Utilities.  Then after the monthly payment on the truck and the insurance etc, that leaves very little left.

As of right now I have no means of getting anywhere.  Where I live there is no Bus service.  So Public transportation is out of the question.  Cabs etc are expensive and since I do not have any money to pay for them, I'm stuck without any means to get anywhere unless I ask friends for a ride.  That is tasking since I live well away from them and is way out of their way just to get me.

I need help please.  As I stated this is my primary method of transportation and I cannot afford trade this in to get something newer and a higher monthly payment.  I need to get this vehicle fixed asap.  

The Shop said that they can fix it for about $515.87, but I would rather have some additional cushion just in case it costs more than that. [See update below]

That's why I'm only asking for $900.  Hopefully that will provide that cushion.  Not to mention the fees that Go fund me will be assessing.  [see update]

I plead for your help.  I thank you for what ever help you can provide.  God Bless.

Update:

Was able to get the freeze plugs fixed, but apparently there was more going on that presented itself shortly after the Freeze plugs were fixed.  

Now there is a head gasket on one bank of the engine that is cracked and allowing exhaust gasses to pass thru into the cooling system.

I drained the coolant system and did a thorough flush to it, then put in a recommended fix, which helped for now.  It seems to be working however, it's not a permanent fix.  

I've spoken to the same shop that repaired the bad freezeplugs and they indicated that they could do the repair but it would cost between $600-$700 if they didn't have to pull the engine out.  

The truck was running for a while after the temporary fix, but I fear that won't last.  

Again, Thank you for what ever you can give and, God Bless.