I won't be able to make it to IDA/ICSID, but I travel often to Taipei so I can give you a few tips.
1. Cost from the airport to downtown:
taxi: 1,000-1200 NTD
bus: 140 NTD
I usually take the Airbus bus, since it stops at most of the big hotels (Grand Hyatt, Far Eastern, etc.) Just make sure to get on the correct one (there are East and West lines). Assuming you are landing in Terminal 2, take a right after you get out of customs, then another right, then a left. The bus station is inside the airport.
2. If you are traveling around town at all, learn to take the MRT (subway), it is a fantastic way to get around (and much faster since it avoids the terrible Taipei traffic).
3. If you don't have NTD when you land, there is an ATM in the airport. ATM's are the quickest and cheapest way to get cash (they typically give you the best exchange rate).
4. Design Sights: If you have time, definitely check out the large Eslite bookstore near Taipei City Hall, lots of interesting design-focused products.