Rep Power: 281

So over a week after taking my car in, I get it back from Honda today with a new headgasket, water pump and belts. I drive around for a while and the CEL comes on and it starts running like crap. It was throwing code 1259-vtec malfunction. I took it back to Honda and the invoice said: low 3.4 volts to oil pressure switch. Rewired vtec in wiring harness. Could driving like this have potentially harmed the engine? Also can you possible tell me what and where they would have screwed this up when they were working on the engine?

I'm wondering if they screwed anything else up because they wouldn't let me pick my car up till 4 days after they finished all the work on gaskets, pump, and belts saying it was running hot and needed a thermostat (even though I got one from them a month ago) and it wasn't running hot before I dropped it off. and that no honda or acura dealers had a tstat anywhere and I had to wait 4 days for them to get one........hmmmmm