1994 Jeep Cherokee Sudden Cut out - Distro? Leads? Ingition

Electrical problem
1994 Jeep Cherokee Engine Size unknown Four Wheel Drive Automatic 95000 miles

CAR IS THE 4.0L one.
Was driving along the other day - normal driving - when the car just suddenly cut out. There was no warning it just cut out. I pulled over and tried restarting it - no luck. The engine would turn over fine, trying, but it would not catch/ignite! The AA came out and had a play with (basically just disconnecting and reconnecting) the wires going into the dizzy. They then pulled out one of the injectors and then put it back in - then the car started. The AA man told me it must have just been a loose connection on the wires going into the dizzy. But it was fixed now!

That evening it cut out again - exactly the same - the AA came out and decided that the problem was there was no power coming into the dizzy from the ingition module and I would need to replace the ignition module.

The next day my mechanic came over to have a look at it. He pulled out the spark plugs and said they (and the leads) definately needed replacing - and that that should fix the problem. But at this point the car was running ok (seemed like letting it cool down solves the problem) He cleaned and WD40's them up and said that should make things better for a bit but they would need replacing asap.

The car then cut out on the way to an exam! (The next day) So he came out to me roadside - a friend picked me up and he took the car back to his (towed it) Whilst I was waiting for him I opened the bonnet and just disconnected, scraped and reconnected the main "lead" that brings power into the distro - then the car started but I wasn't sure how long itwould run for (it was runnign abotu 5 to 10 miles before cutting out on these last few trips)

The mechanic towed it back to his - let it run for a while - no problem.
He says I need to replace the spark plugs (which yes, I do) but I'm not sure they are what is causing the problem. At the moment - this week - I can only afford to fix one thing - and MUST have the car back - the car does need a service but I just can't afford that this month.

I would have thought that the spark plugs/leads would cause one cylinder to stop firing - or they would make the rev's on idle unsteady - neither of this is the case - the engine is runnign sweetly until it suddenly cuts out.

He asked me if I had driven through any puddles recently - I did drive through ione recently - maybe 6inches to a foot deep (it's a petrol) and this could have caused the problem.

My question is: do you think the symptoms match what old sparks/leads would cause?
Or do you think there is another problem - the AA man thought it was something "before" the dizzy, eg the lead into the dizzy or the ingition module.

I'd be very greatful - sorry for the essay ;-) I just need to get the car goign to last me a few more weeks until I have the money to properly TLC it.