Oh, if it's an old-3ds non-xl then he won't do it. It's the most difficult console to do because its clock point is in a really inconvenient spot.
If you trust your soldering skills you can use the guide that @solress linked earlier, but it's not easy.
If you have zero soldering skills, do not attempt. You will permanently brick. The alt clk point needs to be scraped, if you scrape the coating off too much, you will kill the trace.
If you've never soldered before, don't start with a game console. The space on the board is tight and you could easily melt/destroy components on the board permanently destroying your 3DS. I think @hundshamer does non-XL o3DS consoles, but he is backlogged at the moment so he's not taking new orders. You can wait for him to catch up and start taking new orders again.
It costed me either $35 (if I remember correctly). It took about a 8 days of say. This person is totally trusted. I was scared to ship and all, but it all worked out. Aliak11 has done it for many people here on gbatemp. I totally recommend him. It was a nice clean install as well. I'm actually selling the hard modded 3da in the trading forums. Check out the pictures.
