Below are some links with useful information. Give them a thorough read. I've never grown seeds, so take whatever I say with a grain of salt. But it seems to me, summarizing what I've read:

1) Yes, you can collect the pollen in a paper back for later use. However, pollen only lasts a 2 to 4 days. Some say it lasts up to a month in the freezer.
2) Leave the seeds on the buds until they are brown or dark brown and hard. If you harvest the buds for smoking before the seeds are fully mature, just leave them in the buds during drying... they will still mature more while you are drying and curing the buds.



Grow Marijuana FAQ, Cannabis cultivation - marijuana growing tips & photos
Grow Marijuana FAQ, Cannabis cultivation - marijuana growing tips & photos
BREEDING Weed (Cannabis) Growing Guide: