Ok so i have spent several hours looking through some threads and I'm more confused about what I should do then when I started.

I recently purchased a 95 3.4l dirt cheap because it had been sitting for about 8 months, I know it did not sit longer because PO is a co-worker of mine. The car has 230K miles but had a NAPA 3.4L engine put in aprox 38K ago and runs great now that the starting issue is fixed(cord under dash not plugged in good). Put new spark plugs and wires, fresh oil. Immediately the first week of driving it i noticed a lot of vibration, turns out the stupid center carrier bearing was going out. This in turn caused the trans and rear end to leak but only when driving and never on my driveway. In my search for a 1 piece I found a great deal on an aluminumn relatively close. I got it installed and topped off the fluids(rear end was very low and took an entire bottle before it was full) which improved the ride substantially. However now that the drive shaft isn't making a huge ruckus and vibrating the hell out of the car i notice when taking off at about 3/4 throttle or higher it bogs down a bit and feels very rough, I thought it might be the rear end but im not sure(it does have 230K miles on it).
To make things worse the pinion seal is leaking slowly now that it has fluid to leak out.

I'm confident I can replace the seal myself, however there is no point if I will have to swap the rear end out in the near future anyway.
I have not yet pulled the cover off to look inside and plan on doing that but it has been too nasty outside the last week and the weather doesn't look like it will clear up anytime soon.

I do not think the rear end has had the proper fluid level in awhile, however it does not have the 'normal' signs of wear that I have seen listed, there is no other problem except when getting on the gas, and the slow leak. Transmission runs like a champ(it has about 120K mi) so i don't think it's that.

Does anyone have any suggestions or confirmation that this is in fact the rear end and not something else.

If it is, what camaro models/year can i steal one from that would be compatible. a lot of 3.8L in JY here but no 3.4L.

I have gotten check engine light off and on but unfortunately its the reject obdII connector with OBDI unit.

 

im thinking you didnt notice it when it was vibrating. could be a number of things so finding what the codes are may save a fare amount of funds. if you have an obd1 scanner you can do this http://shbox.com/1/xraycable.jpg

 

As far as rear ends go, just about any rear end will work, but look for one from a 95 or later car so you can retain TCS.

 

That is a nifty trick, I will have to try that if i can find someone with a OBDI reader. Yeah im pretty sure it was like this all along, there is no way i would have noticed over the ds vibrations.

I think I will prob go ahead and change the fluid in the rear end out and see if its 'destroyed', if it's not i might as well change out the pinion seal while im down there. Hopefully sometime in the next few weeks i will get a sunny day to work on it. For now it is staying parked unless my Jeep takes a crap.