Why A/C blowing hot air?

Hello, ive checked for dye and oil , nothing visible..Before ive charged it rwith the r134a something pro..i dont remember the whole name, bit its in a black can, i smelled alittle oil burning, but i doubt that it was the a/c, my car was over due for an oil changed. After changing the oil, the smell went away. IF it is a leak, is this an expensive repair if i decided to go to a regular autoshop instead of the dealer? Also, my windsheild wiper doesnt spray washer fluid, and i fulled it up, no leaks the blades still work but when pull the lever for fluid i gets nothing not even a sound...