I have a mod'd Wii and no real issues with it. My only issue is with SuperSmashBrosBrawl which has special copy protection, where I need to open up my Wii to find out what chip I have and update its firmware but I've been too lazy to get around to that (plus I don't have a triangle screwdriver).
For chip + installation I paid 45,000 colones but I think it's about 55,000 now.
For games they are usually 2,500 each - but I just download and burn my own DVDs since the stores here seem slow on getting the newer games for Wii.