Yes rain will damage the servos but only if they get wet inside and start to corrode. If they haven't begun to corrode just a bit of a blow from a hair dryer or heat gun on very low will probably save them. As far as the airplane is concerned check to see if anyof the main construction got wet. Once balsa is thoroughtly soaked it is easily bent, that's the reason some sheeting is soaked with water/ammonia to help you bend it around a curved surface. Check your receiver too. Same applies to it as the servos. If possible remove all the electronics and test them on your bench after they're dry. The airplane will dry by itself is kept in a reasonably warm place, not hot. When it is dry check everyting for alignment. Unless it was submerged in water it will probably dry straight.
If you find a warp remove the covering at those places and hold the warp straight while you recocver.