The voltage regulator is in the alternator, it is a series of diodes and they are probably fried. On this side of the pond there is a fairly good industry of auto electric rebuilders in most major locations and these can rebuild the alternator at competitive prices vs a rebuild. The advantage is that the rebuild is individual instead of assembly line in a large rebuild factory. Both options are less expensive than buying new.
The radio does have an internal fuse and it's likely this will need attention.
In addition to the fuses, there are relays which should be for the most part unphased unless their appliance was turned on. There are also a series of what Porsche calls Current distributor links, essentially fusible links, which connect certain circuits directly to the battery. On US market cars, this current distribution block is located in the right side footwell. The positive battery cable connects to it on the 'frunk' side making it easy to locate. There are 7 of these fusible links and I suspect some of these blew and caused the smell you experienced. So far as I know, these will only be available from the dealership. On the '04, there are 2 links for PSM, 3 for the OBC (On board computer), one for the ignition lock and one for the engine electronics - some or all of these may have been affected. These can be individually checked with a DMM (digital multi-meter) using the continuity function.
FYI, most vented batteries have a plug on one side which can be pulled and swapped with the open vent hole on the other side to allow installing the battery in either orientation. You simply pull the tube off, remove the plug from the other side and swap them.
Good Luck!
