Why don't you just take it in to an air conditioning shop and have them check it out? It can't cost that much compared to burning up can it?
I've read many comments in this forum that you shouldn't change the freon over to the 134 if you can help it. Why did you change it over in the first place? Maybe your friend missed something in the process and he's over his head, "this isn't a Caterpillar..." I know how favors can back-fire on us.
Anyone else have an idea?