1996 Mitsubishi Montero maintenance-required light on and blows smoke

1996 Mitsubishi Montero mileage: 84,000. I have three problems to address: 1. When I start the Montero I usually hear the lifters making noise until enough oil is circulating, is there a way to stop this? 2. Sometimes it blows smoke at idle or slow speeds, it doesn't do this on the highway and acceleration has always been very good. 3. I have a maintenance-required light on, I truly believe I hit a pre-established mileage and the light came on, is there a way to extinguish this (a switch or something?)