Digital Signatures common practice

[Paul V]

I develop stencils and templates with macros. Right now I
instruct customers to "Enable Macros" when opening them.
I am contemplating digitally signing the macros assuming I
can then tell users to "always trust my macros" once and
never be bothered again. I'm a newbie at this so...

1. Will "accept my macros" prevent the dialog box?

2. Do others commonly do this?

3. Are there any "gotchas" for me or my users?

4. It looks like you get certificates from Verisign
($400/year) or Thawte ($200/year) and that Thawte is owned
by Verisign. Are there others and why is Verisign 2x
Thawte price.

5. What else should I be asking that I'm not smart enough
to ask yet?

Thanks.