HELP PLEASE

I am sorry for NOT searching for this problem first.  I will do it after I post this thread.  

I am confused.  All of a sudden my touchscreen turned BLACK.  I didn't drop it in water or drop it on the ground.  I did change my microSDHC card to a bigger capacity one.  I also took out the battery and put it back in.  When I get home from work I put my cell phone to charge on the AC adapter.  

I did get my digitizer replaced for $75ish since my touchscreen didn't work right.  

I have brought my BAD cell phone to a repair shop.  So far they have replaced my LCD screen and flex cable with NEW parts but nothing has changed.  They are ordering MORE parts.  According to the repair shop my repair cost will be about $95ish.  I have already paid a $50 deposit which applies to my repair bill.  If I don't decide to continue with my repair then I have to pay $35ish.  

My cell phone plan expires in December 2011.  I am debating on continuing with my repair or just buying a temporary cell phone until my plan expires.  

Please advise me.  Also if someone has the same experience then please let me know how you resolved the situation.  

Thanks in advance
stteng

P.S. Do I need to perform a HARD RESET on my phone?  If so then how do I do it and what do I need to do to prepare for it?