No spark equals a bad crank sensor.
You can buy one at AutoZone.
Located on the drivers side, back of engine half way down.

 

How tough of a fix and what kind of cost am I looking at?

So, something needing to be reset after to battery and alternator have been disconnected has no merit?

 

http://www.roverparts.com/Parts/ERR7354G.cfm

The only thing that may need to be reset would be the alarm and the stereo.
Lock and unlock the drivers door three times with the key and then see if it will start.

 

How difficult of a change is the crank sensor? Any chance of a picture showing where it is?

 

The crank sesnor can be easy or hard to replace. All depends.
Drivers side of engine, half way down on the back of the block.

 

Just for the heck of it, lock and unlock your truck 3 times. Then lock it, while holding it in the lock position for 5 seconds, then unlock.

 

oops, reverse the lock and unlock. just lock it and unlock for 5 seconds.

 

Just in case, check for spark on two separate spark plugs so you can rule out a bad coil unit. Generally, when you experience a stall due to a bad crank sensor - the vehicle will not start again until the sensor magnet is totally cooled down (ie - an hour). The fact that you were able to restart right away tends to have me think it's not the crank sensor. But a bad coil unit caused by a bad voltage regulator on your old alternator, would tend to make a bit more sense imo...

 

rule things out... youre cranking, so it isnt securty related, if it were, youd see the red led stay on solid, and youd have a nno crank situation. now, when youre cranking does the check engine light go out? if so, youre looking at coil... if not, its one of two things, immobilization or crank sensor. as suede said, and given the low voltage conditions the cars been through lately, id say crank sensor prbably isnt the fix. the ecm has a stored code in it that it compares to a code in the bcu, if the codes dont match, the ecm doesnt spark the coils. the immoblization needs to be reset by someone with a testbook, simple to do, just need the right equip.