1994 Toyota Corolla loads of symptoms, need diagnosis

I have an old Corolla wagon with 217000 hard miles on it (temps between -50 and 120, 8 northern winters, 3 years on the FL coast, 3 accidents, dozens of trips across the mountains loaded with gear). It's run flawlessly this whole time, and except for tires and oil changes it's had very little work done it. It started running rough in cold weather about 5 years ago. Luckily it only drops below freezing a couple of days a year here. Lately it is running very rough at idle (not stalling), making a horrendous squealing sound in the morning when steering (stops after a few minutes), making a rattling noise from mid-car below my seat for about 2 seconds during hard accelleration, making a burbling exhaust sound from mid-car at idle, and yesterday I blew out clouds of whitish smoke for a few minutes after starting the car (it was warm and no other cars were smoking so it seemed odd). Can these symptoms be related? Are they easily diagnosible? And most importantly, do any of them indicate a problem that should make me stop driving the old girl until she's fixed?