No neighborhood would be complete a Dry cleaning/Laundry/Alterations (clothing mending) shop.
The turnaround time at the local shops is often 1-2 days and prices are very affordable. Any type of alterations is possible, including shortening pants/jeans while retaining the original hem line. Such service are typically under 15,000 Won ($10.50USD).

명품세탁 전문점 – (myeong-pum jeonmun-jeom) Luxury/high quality laundry specialty shop
수선 전문점 – (suseon jeonmun-jeom) Alterations specialty shop
Here’s our related arricle on running errands.