I'm new at this so if its already asked sorry to waste anyones time but:
I flushed a toilet tonight and one in another part of the house started gurgling. I've never had that happen before. We are on a septic system so I'm really hoping that it isn't a septic system problem. We've just redone the roof including replacing all the vents. I've also noticed an occasional 'sewage' smell coming from my kitchen sink. I'm hoping it's just a vent, not a septic issue. Any help would be so much appreciated.
Sounds like you have a partially blocked vent. The system has to get air for the water to flow, if the vent is clogged, it will pull it from toilets, sinks, etc. This causes toilets to gurgle, and sink traps to be sucked dry, allowing sewer gas to escape.
When was the septic tank pumped last? HOw often you should pump out the tank is and educated guess based on family size and how often it was pumped ou in the past.
A pumping company rep should be able to tell you about problems in your septic system/
The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.