need to consider some alternatives to replacing a shadowbox built-in-place cedar fence

I want to continue to have a cedar fence, so metal replacement it not a consideration

other than tearing the whole thing apart and building a new one, couple questions
(will think of more later)

1. are there any specific tools (other than a hammer) to make removal of old nails
easier if I wish to remove old boards where the posts are good and nail new boards on
(am asking specifically about making removal of the old boards easier)

2. if a post is wobbly but wood is good, can a new cemeted post be placed next to it
to secure the post

3. will regular home depot or lowes cedar boards work or do they come in different
quality grades

anything else I should consider to make repairs easier?