Kia changed timing belt and after driving car home it wont start.

What is your question?

My car was working fine. I drove it into kia to change the timing belt. I picked it up and drove it home after the job was done. When i next tried to start it the battery was dead. Husband charged it, briefly started with a bad drain, very rough idle and check engine light on code po300, random misfire detected. Kia towed it back into their shop. They say they did a check on battery and it was ok, but it needs new fuel injectors. Icant afford putting anymore money into it. I feel it sounds fishy that the car was otherwise fine when i drove it in for the new timing belt and now all this. My husband thinks they were one notch off in adjusting the timing belt. I think i want to tow it back home. It wont run correctly on its own. What is the likelihood that they are being upfront with me on this?