sidewinder 6500hf won't respond

I have the above alarm system installed in my 96 Impala.  The other day, the brain seems to have stopped responding to the transmitter.  It worked fine all morning, but in the afternoon, I went to lock it with the FOB, and nothing.  The system would usually self arm, but it also did not work.  So currently, the system is inactive.  Any thoughts? 

I purchased the car used with that alarm system in it, and have no manuals.  I saw the owners manual is still on DEI's website, but I was looking for the installation manual as well.  I don't know all of the features that the system may have or have been installed. 

If the alarm is toast, I'm looking to replace it, and right now, the current front runner is the Viper 5601.  But so far, no one (retail tech support) I've called can give me any clear answers.  Like will the 5601 work like the 6500HF?  Do I need to purchase more modules beyond the unit to make it work with the doors/trunk and starter? 

I know there's a lot in this post.  Any help would be appreciated.  Thanks. 

Nothing, the LED in the car is doing nothing.  The light in the FOB is fine (replaced the battery thinking that was it).  I was going to edit my post this morning with that little bit of info. 

Once the weather gets nice (its been raining everyday for a week straight), I'm going to take apart the dash, and dig into the brain and wiring a bit.  See if maybe a fuse or something is blown.  I did call a local shop, and explained what happened, and he mentioned that maybe the antenna went, which is integral to the brain on the older units, not a remote like the newer ones.  But what doesn't make sense, is why the LED is out, and why nothing seems to be working.  Would the system completely shut off like that if it lost the antenna?

No, never found an installation manual.  I agree, can't find it anywhere.

I still can't figure out what happened to my system.  Need to dig into it a bit more now that we have some nice weather finally.

So I took some time over the long weekend, and removed the brain from my car.

I opened the brain unit itself, and didn't notice anything out of the ordinary, scorched lines on the board, blown circuitry, nothing.  But I looked back at the plug end of that 12 pin, and the 12V lead in the plug looked like it had gotten hot. 

So, I'm thinking something shorted out that lead, and without 12v of power to the unit, it didn't work.  So...does anyone know where I can get a new pig tail?  Or perhapes have a good source for some of those plug ends, and I'll pull all the pins out of the old one, and re-pin a new one? 

Just trying to save some cash, don't feel like putting in a new system if I don't have to.