89 cherokee a/c ? How can i tell if it has been converted from r-12 to r-134a?  WHo sells complete kits to convert, o-rings compressor, hoses ect.  

It is easy to tell because if so it will have R134 adapters on charge ports. I STRONGLY advise against such R134 conversions though because you will loose cooling capacity as R134 is not as efficient and develops higher pressures too. New R134 systems are designed with this in mind. Besides, R134 is set to be banned in 2012 too. (it is actually quite poisonous) I would try R12a. It is hydrocarbon based and cools really well (even better than R12) Heck you could even use Propane in it and it would cool better than R134. Also R134 is not compatible with mineral oil in a R12 system so you have to add more oil to it (PAG oil) to bond to R12 oil and R134 which lead to potential for a oil overcharge and further loss of cooling. R12a does not have any problems with R12 oil and R12a is very big in Australia.  

can i purchase this at checker or autozone, i need to now take back the now useless r134a leak detection kit!  

You can get R12a on line but it is technically not EPA approved so most stores do not sell it. Their argument is that it is a flammable agent (even though it is in a sealed system and your gas tank contains 500 to 1000 times more fire energy potential) I think that politics plays a bigger roll here because R12a is not poisonous (neither is R12 but 134a is) and it is very environmental friendly because it breaks down in about one year if released (R12 is bad about this and 134 as it turns out is not as safe as DuPont suggested) They say if there was a leak R12a could cause a fire in A/C but it would have to be a big leak and you would smell it long before it was a issue plus there is not much in it (about 18oz's by weight) But what they do not tell you that if R134 leaked into a fairly well sealed passenger cabin that it could be lethal. Also since R12a weighs about 1/3 as much by mass yet has more cooling ability for this same mass it takes less power to compress and use it. Old R12 is a tuff act to follow because it was a perfect refrigerant other than environmental impact. And the silly part of that ban was that cars were a very very small part of ozone problem from R12. The real problem was than R12 was used for many years making Styrofoam products and releasing tens of millions of tons of R12 annually into atmosphere. In order to banned that they banned it in cars too. Still no word of a approved replacement for R134 after 2012 but I expect it to me something of the nature like R12a which has a lot of support overseas.  

has there been any big problems with r-12a fires, and can i buy r-12 online also, as i would rather recharge it with a better refrigerant, as it is 120 almost everyday where i live in the summer.  

There has been no fires that I ever heard of and BTW, R134 will burn too on its own if it get hot enough and the gas from burn is even more deadly. You can get R12a on line or on Ebay (it is sometimes called ES-12a too). And like I said, you can even use Propane if you want too as it works well too. One more thing, even if you had a leak, there is about 15 to 18,000 btu's of heat energy in it to support a fire vs about over 2 million BTU's of heat energy in gas tank. Which one do you think you need to worry about more?