SimpleG, is it REALLY for your friend? Not for yourself, right? ;-) :)
1. How long will it take her to get a work permit once she marries him? She has 2 more yrs to complete her education and wants to be able to get her work permit before finishing so she's able to work.
Currentlly, the Govt. is processing May 2000 applications. This means there is nearly 3.5 to 4 years of waiting period. Your friend will have to hang in there with her F-1 then OPT, or her own H1. (http://travel.state.gov/visa/frvi_bulletincurrent.html , family based PR's spouse's priority is 2A)
2. Will she have to change her visa type from F-1 to something else upon marriage?
She needs to apply for permanent residency right away. Then wait for nearly four years to hear from the immigration dept.
3. How long will it take for her to get her permanent residency (greencard)?
See above. Nearly four years.
If HE is eligible to apply for citizenship, then it takes about 4-6 months to get his citizenship. Then SHE can apply for permanent residency and work permit.
(There is a little complication regarding applying for permanent residency now, and during the four years of waiting period keep applying for temporary residence visa like F-1, OPT, or H1. You see there is a conflict. But I think the Immigration Dept. has been more flexible nowadays.)