CJJ

Hi! New to this website and new to owning a Subaru. Purchased a 2005 Legacy 130K about 5 months ago knowing the timing belt needed to be replaced. Brought it to the Subaru dealership and had that done 10 days ago... they also informed me the brakes needed to be replaced... got that done and they also did an oil change.... since then the car hasn't been accelerating very well and running kind of funny and CEL has been going on and off... called dealership today and they say to bring it in. On my drive the CEL comes on and stays on (for the first time since owning), in addition to that the cruise light blinking.. they run diagnostic and tell me some spark plugs/gasket (I think) needs to be replaced.. say it's going to $400! but tell me they'll split the cost since I was just there for work... So, they do that. I go to leave dealership, start the car and it's idling super high/hard, at oil temp starts flashing and the car dies. I walk back in and they all look super confused. tell me they need to keep the car today/tomorrow and give me a rental to use. The car drove just fine prior to bringing it to the dealership and now new symptoms keep coming up. I don't know much about cars... any info/help would be greatly appreciated! thanks