Please help Poor fellow replace Spark Plugs/Maybe Wires

Hello All,
I need to replace my Spark Plugs, and my wires. I notice the front 4 seem to be a breeze, but I cant even see but one of the back 4. (Even when the big plastic thing that says Cadillac, where most breather covers are, is removed) I have had so many problems with this car its unreal.
For starters, right after I got it 3 years ago, it fouled 3 plugs. I had been told that the Water pump was replaced when I bought the car. I took it to a local mechanic, who charged me 180 bucks, replaced 3 plugs, then tells me that the head gasket is blown and it will always foul plugs. This scared me to death. Then after coming here, someone told me it was probally seepage, that they had probally used wrong anti freeze, and not replaced the pellets that go into these cars cooling systems. I did as they suggested, and no more anti freeze smell, no more fouled plugs until now, 3 yrs later. About a year ago, the car was shut off to fill up with gas, when I tried restarting, it was dead as a doornail. I had it towed, and they said the Alternator was shot. I paid them well over 300 dollars for a new alternator. At the time, the mechanic told me that he himself had to return 3 altenators before he got one that wasnt defective from Car Quest. Well a few months ago, that alternator shot craps. I had 3 disabled people with me, we were in St Louis at rush hour, and the car kept telling me Battery not charging. I called my mechanic, he tells me to try and make it home (almost 60 miles) well needless to say, we made it about 8 miles and battery was drained. The disabled folks I had taken to the Dr had to set there nearly two hrs before we were towed home. Well they replaced the Alternator for free, but less than a week the replacement Alt went out again. Now the Alt seems ok, other than it reading all over the place, for instance, it will be at 14.5 when I start it, then go down to 13.2 then up to 13.7, then down to 11.9 all over the place, it never did that with the origional alt. Also, I think from it being driven when the battery was so dead, it fouled out more plugs, cause now its backfiring, and cutting out, and its once awesome gas milage has gone way down. Also, they had repaired a broken brake line, had to remove the gas tank for that, charged me 400 bucks, and now, the automatic air shocks or whatever, are constantly filling themselves up, making this horrid noise, that it never did before. When I told the mechanic about all this, he tells me it's "normal" I know it isnt. I want to try and change the plugs and wires at least, to see if that helps the cutting out and gas milage prob. Can anyone tell me how to get to those back plugs? And what plugs and wires do you recommend? The wires on it say "Packard" I figured they would be Delco. I myself am disabled, I have had several back surgeries, and cant stand up for more than 15 to 25 minutes, but I thought if I quickly got those 4 front ones changed, then did one at a time on the back 4 before it gets too cold outside, maybe I can do it. I need to take everyone back to St Louis in 3 weeks and am frightened to take them with the car running like this. Any help would be greatly apprieciated. God Bless you. Jack