1) i think the package you are looking for is "ppp" (ie: yum install ppp), it is for centos at least..
2) my centos gateway doesnt have a pptp.conf, so im not sure on that one.. maybe its not used in RHEL based distros?
3) man pppd explains the command line options, i believe they are the same as the "options" file, mine is virtually empty.
4) chap-secrets contains the username and password (as they would be set in a DSL/etc modem) seperated by a tabs and an "*"
That was all i had to set up for my home aDSL1 connection, but there may be some non standard settings depending on ISP