My advice would be. Given this statement by your "technician' "told me that the motherboard was rusty." that unless this was not the 1st instance of spilling some liquid on the laptop i would steer well clear of that particular technician. His portrayal of the cause and effect of the liquid incursion into the innards of the computer significantly exaggerates the process of oxidization. If you have the patience i would suggest you, within the limits of your ability, remove all covers/doors/access ports on the computer as well as any easily removable inner components and then give the unit time to dry (could be a couple of weeks). If you decide to use a device for accelerated drying such as a hair dryer. Use caution and use it only on low speed and hold it at least 2 feet away. If the Gods be kind and smile on you you may recover the computer. Competent repair shops can do this service but will need to be measured against the cost and possible negative result.good luck,truenorth
