Oh boy will they smell ! And they usually find a nice warm place to die near pipes etc, its a charming rotting cabbage-style odour :-(
We suffer from them every winter , we never put poison down , the best way is old fashioned traps. You can buy very good pre baited plastic traps from Woodies, much easier to set than the wooden ones , and believe me just as effective.
Keep an eye out for areas with droppings and place your traps there. I dont believe in the plug - ins at all , I once seen a mouse standing right beside one! I think they become accustom to the sound, otherwise mice wounldnt be in industrial places etc if they were repelled by noises.
I find peppermint very good , supposedly they dont like it much . I have a little plant in the kitchen , and bought peppermint oil & sprinkle it in areas I'd usually hear them , and i havent heard/caught as many this year as I usually would of.
Good luck hunting !