If you can find the relevant bits in two separate programs (reading the ADC and writing the LCD), then you should be able to combine them.
Since you're "on chip", then everything is highly specific to your particular hardware setup, like how everything is wired together, what tools you're using etc.
It's best to work on small bits of code at a time. The scope for messing things up is pretty high and the means by which you can analyse what went wrong are very limited.
Like I said before, you've got a nice LCD display which can be your friend when it comes to debugging. So getting that bit right first will make the next steps a lot easier since you have some chance to use the LCD for debug as well as output.
