That Car Or Not That Car, That Is The Question

Well, my car may not be as bad as it first looked.    Ben, the mechanic looking at it, said that the problem was "the crankshaft position sensor, aka the ECU doesn't have a clue where the engine is ever at in it's cycle, and thus doesn't know when to inject fuel."   The part for the sensor is only $50 plus tax and shipping.   Plus the cost for Ben's time and work.  But, it is a lot cheaper than I thought.  He also thought that this would fix the shaking/vibrating of the engine.      

So now I am in a dilemma, that I would love prayer about.  I have a handful of options right now.   

1. I could keep my car and hope and pray it doesn't break down again
2. I could sell my car and buy the one that I am driving now (valued at about $3,500 but the owner offered it to me for $2,500)
3. I could sell my car and buy my mom's car for $4,000 (a nice, low mileage car that has a wonderful history (it used to be my great aunt's)  and was well taken car of) 
4. I could sell my car and look for another Toyota Echo either in Texas or to import from Canada (because it would be cheaper - possibly)
5. I could sell my car and look for another car

If I would sell my car, Ben has expressed interest in buying it.  I could probably get $1,500-$2,500 out of it.    I currently have less money to spend in my bank than what is actually there - I over spent on my credit card (intentionally) on coins - That's another story in a different post.   I hopefully will have a few hundred extra soon though.  Either way, I likely would have to take out a loan to get either the $2,500 or the $4,000 car - both of which I would like, though they are downgrades to what I have (even though they are 1-2 years newer and have 150,000 - 200,000 less miles on them than my car has).  

I would appreciate prayer on wisdom in making this decision and with timing as well.