If you're making substantial changes, you would present the whole new document for approval. That is called a bylaw Revision. If you're just changing specific sections, you delete the old language and add the new langugage. You can make up a chart for the members that show the old vs. proposed language, but the actual document should be "clean" and current. We add a little tally at the end listing the date we adopted changes, but we don't keep the old language in the body of the bylaws.
Depending on your group's perception of your bylaws, and the state of your bylaws, this might be a great time to do a wholesale review and restructuring. We did a major revision about 4 years ago. I sat on that committee and thought our bylaws were "perfect". But now, years later, when I read some of the verbage I wonder what we were thinking! So...here we are with another bylaw committee tweaking some of that perfect language and revising content to better match our reality. We're making them easier to understand so our members can acutally refer to them without a law degree in hand.
Roberts Rules specifies that a wholesale bylaw revision must be presented to the membership in advance of the vote and then adopted by a majority vote. Subsequent individual amendments must also be presented in advance and approved by 2/3 vote (unless otherwise specified in the bylaws themselves).
Regarding putting the actual dues amount in the bylaws. I would caution against that since the amount is binding until an amendment is approved. Our bylaws specify that the dues amount is set by the Executive Board. This clever language gave our board the right to set dues to $0, thus eliminating them and making all our parents and teacher automatic members. I'm not sure the original writers realized the power of that clause, but it worked well for the leaders of the group and in the end, the whole PTO. If we ever need to reinstate dues, the bylaws are fine, and the Exec Board just votes to set a $ amount.
