I don't think the hard drive swap would work, due to how the PlayStation is with swapping hard drives. I'm not entirely sure about what you're trying to do, so maybe someone more experienced can come along and confirm or deny if it would work. I haven't down a hard drive swap yet, as I have had no need to so far.
If the HDD swap doesn't work, (and if you trust him to the end of the earth) here's how he can get your 50+ PSN games (I know some people do this, but I haven't done it and I don't plan to):
1. Remove all the payment information on your PSN account, and set up a temporary password.
2. Get him to make a new user account on his PS3.
3. Give your PSN information to your friend, and have him log in with your info under his new user account.
4. Tell him to go to the download tab and get the games he wants. The games, once downloaded to the hard drive, shouldlet him use them under his own user account, since it would be using the games section of the hard drive. After he's done, sign in on your PSN account under your machine and change the password back and re-add your payment information.
If he upgrades his hard drive he might have to re-do this process to get the games again, as the back-up utility might not save the games themselves.