everything you did at 90k should be done at 180k as well...i would take care of that asap.... im actually surprised that you've now made it 110k w/o changing it... i suggest you do so

-realistically it differs between cars... i've seen them go @ 85k and i've seen them go at 130k (w/o changing)

-no warnings, it will snap, or jump a tooth and you can kiss your engine goodbye

-yes they should be able to... but they will try to talk you into getting the service done there which costs close to $1000

.....i would suggest changing it for that trip.... just to be safe... that's a long way to go with being "unsure" about the condition of your engine