Man you guy's are misinformed. First off, if you want it (or anything) done right, DON'T take it to CT. I don't mean to bad mouth but I have seen many shady things come from there. Find a nice little local independant shop.
On to AC. Its not rocket science. You don't change compressors, seals, hoses, etc to retrofit to 134. We litterally put new fittings on the old ones so our AC machine hooks up and add a special retrofit oil. Thats it. Recharge, add leak detection dye, leak test and your done. Ya it costs 2-3 hundred bucks but thats the price to do it the right, and legal way.
Those DYI flamable freons do work and nothing wrong with them except no shop (reputable shop) with an ac machine will hook them up and service or repair components due to conamination to the machine (unless the system is completely empty).