Who ever told you that it will cost $1500 is really getting his hose out. A rebuilt compressor from a parts house shouldn't cost over $300. The conversion to R134 is about $75.00 in parts. On the very out side if you do the work, $500.00 If an A/C shop without a hose should be about $800.
Even if you put in anew A/C the truck is still work about 2K but can you replace it for $2K? So the decision is up to you. Good luck