Unfortunately, there's almost nothing you can do. Most adapters used today are sealed and cannot be easily opened without damaging them. Also, there's a good chance that the adapter doesn't have a fuse and that the voltage regulator itself died. There's also a chance that other components could have been damaged, like capacitors, diodes and so on.
If you can't find an adapter with provided capabilities, then go for one that can supply higher current. 1.5 A is the minimum current you should look for. If you can find better, go for it.
Also, be sure to check for more modern adapters. Switch mode power supplies which can work form 100 V to 250 V and from 47 Hz to 63 Hz aren't very rare, so you may be able to get one.
As for repairing the adapter yourself, I doubt that you could easily do it. You'd need to find an electronic component store and get the spare parts, if they do have them, and then fix it, which can turn out to be extremely difficult. Plus, there's the needed equipment. Electronic component stores usually sell power supplies which provide standard voltages such as 12 V, so that could be a good direction to look in.
The last option is to order an adapter from some web store such as digikey, mouser, farnell or someone who sells consumer electronics. It seem that Farnell has a store in Philippines.
As for router damage, it's difficult to say if it is damaged or not. Unfortunately, there's nothing you can do until you power it on or open it. If you do open it, you could look for standard burn marks, visible damage, do continuity tests, if you have a multimeter and so on, but even if you do all that, there's no guarantee that the router will work once you connect the new power supply.