Yes you should update to HEN on 4.87 HFW. Your games will be fine, dev_hdd0 will not be touched when you update.
HEN is much better than HAN in lots of ways. You can run Homebrew and plugins like Multiman and webMAN MOD, so you can have stuff like background FTP access to file system, run ISOs from external HDDs, Run emulators like Retroarch. It can do almost everything that CFW can do compared to HAN.
Just install 4.87 HFW then go to http://**ps3xploit.com >Domain no Longer owned by team** (ps3xploit.me =new)/hen/installer on the PS3s web browser to install HEN.
More info here