My cat ran away a few days ago he came back with diarra and I gave a bath I thought he had worms?

But he had maggots . i called my vet he said the same thing I read all over the web to shave him than pull them all off , and bring hem in on Mon,because I could not pay the $ 200.00 ER fee.so what my question is as i was cleaning him,I push on his tummy ,and hundreds of them came out his .My my friend said that means it is to late to save him ,even if I took him to the vet asp . She said once there inside them it means they have eaten through something to get in side ,and there to deep to clean them all out ,or there blowflies maggots or some thing like that and you can not get rid of them unless its caut very early. Is this true is my cat going to die no matter what i do not even a vet can help? Sorry about my spelling but I'm crying pretty hard right now. Please tell me the truth I would rather know than not . Thank You