vi is installed by default, and you should be able to access it by typing 'vi' or 'vim'.
Actually, for no other reason than pointless knowledge, almost any unix system you'll ever see will have vi available, so it's a handy one to know how to use.
As for your question, try this. 'cd' to your /usr/bin directory. Then 'ls -l vim-enhanced' If you get nothing, something went wrong in your install, because vi/vim (vi iMproved) should be there by default. If it is there, then you need to edit your path to make sure that /bin and /usr/bin are in it, and make sure there are links to vim-enhanced in a directory so that you only have to type 'vi'. Of course, you can always try installing it off your cds or the internet, which is probably easier.
For the record, I'm using mandrake at this moment, and it's a cherry install(I tend to dink around with a lot of different distros so I can help out here), so I'm not just guessing.