As far as checking them goes, if you get smoke on startup and idle, but not during normal driving, then the seals are probably shot. The theory behind this (if you're interested) is that during idle, engine vacuum increases and if the seals are worn, oil can get sucked down past them into the cylinder.
There are two replacement options. You can do it with the head on, but you will need to stop the valves falling into the cylinder when you release the keepers, so you either pressurise the cylinder with compressed air through the spark plug hole, or fill the cylinder with nylon rope through the same hole. You might also find access a problem as you get further back towards the firewall, so you may need to pull the hood and cowl.
The other option is to pull the head and replace the seals on the bench. And if you've got the head off, you might want to consider a full valve job if the motor has 207k miles on it.