I did some checking using one way full Y fares and current LP international schedules. It basically becomes the travelling salesman problem, trying to minimize the amount spent with some constraints, like start and end point and the MIA-MGA requirement. If you are not bound by having a continous schedule the minimum would be around 1800 dollars to fly the cheapest international segment on each airline and LIM-CUZ-LIM. You then have to add the 3 flights on KL/US/TW plus the car hire/hotel requirements.
However, that leaves you with a lot of unconnected flights (eg the cheapest Aeropostal flight i could find was CCS-CUR - nice, but how to get to CCS or from CUR).
Using MIA as starting point and Lima as finsihing point I got around 2400 USD. However, I am sure that with a good travel agent, using lower fares and multi-segment tickets (assuming LP allows these) that can be brought down.
Again you have to add the other costs, plus airport taxes, plus transfers to/from hotel and for those of us not living in the region the cost of getting there.