Jan,
Here are some good links to research:
<http://www.shaunakelly.com/word/styles/TipsOnStyles.html>
<http://www.word.mvps.org/FAQs/General/FindingSpecialCharacters.htm>
<http://office.microsoft.com/en-us/word/HA011876141033.aspx>
<http://www.google.com/search?&q=paragraph+character+style+format+ingroup:wo
rd>

Maybe this will help? It will allow you to pick a style from those available
and replace it with another picked from those available.

Sub ReplaceStyle()
Dim FindStyle As String
Dim ReplaceStyle As String

FindInput:
MsgBox "Pick style to find", vbInformation, "Find Style"
With Dialogs(wdDialogFormatStyle)
   .Display
   FindStyle = .Name
End With

ReplaceInput:
MsgBox "Replace " & FindStyle & " style with which style?", _
vbInformation, "Replace Style"
With Dialogs(wdDialogFormatStyle)
   .Display
   ReplaceStyle = .Name
End With
   Selection.HomeKey Unit:=wdStory
   Selection.Find.ClearFormatting
   On Error GoTo FindError
   Selection.Find.Style = ActiveDocument.Styles(FindStyle)
   Selection.Find.Replacement.ClearFormatting
   On Error GoTo ReplaceError
   Selection.Find.Replacement.Style = _
   ActiveDocument.Styles(ReplaceStyle)
   With Selection.Find
       .Text = ""
       .Replacement.Text = ""
       .Forward = True
       .Wrap = wdFindContinue
       .Format = True
       .MatchCase = False
       .MatchWholeWord = False
       .MatchWildcards = False
       .MatchSoundsLike = False
       .MatchAllWordForms = False
   End With
   Selection.Find.Execute replace:=wdReplaceAll
   Selection.Find.ClearFormatting
   Selection.Find.Style = ActiveDocument.Styles(ReplaceStyle)
   Selection.Find.Replacement.ClearFormatting
   Selection.Find.Replacement.Style = _
   ActiveDocument.Styles("Default Paragraph Font")
   With Selection.Find
       .Text = ""
       .Replacement.Text = ""
   End With
   Selection.Find.Execute replace:=wdReplaceAll
   End
FindError:
   MsgBox Prompt:=FindStyle & " Style does not exist", _
       Buttons:=vbExclamation, _
       Title:="Error!"
   GoTo FindInput
ReplaceError:
   MsgBox Prompt:=ReplaceStyle & " Style does not exist", _
       Buttons:=vbExclamation, _
       Title:="Error!"
   GoTo ReplaceInput
End Sub

The solution I proposed first seems to work just fine.
If I go into one of the Normal style paragraphs with bullets, and "select
all 2 instances", I can then appy a bullet style (odrazka-popis-pole or some
other style).

If you want to find all paragraphs with this bullet, no matter what style is
applied, you can use something like the two code samples I gave in my first
reply, say like this:

Dim myPara As Paragraph
For Each myPara In ActiveDocument.Paragraphs
 If myPara.Range.ListFormat.ListString <> "" Then
   If Hex(AscW(myPara.Range.ListFormat.ListString)) = "F0D7" Then
     If Selection.Range.ListFormat.ListTemplate.ListLevels(1).Font.Name =
"Symbol" Then
       ' next two lines just for debugging:
       myPara.SelectNumber
       MsgBox "Here:"

       myPara.Style = ActiveDocument.Styles(wdStyleListBullet)
       ' ... or apply some other of your styles
     End If
   End If
 End If
Next myPara

The "bold" is then applied on top of the style as manual formatting...
something that should be avoided.
An occasional bold or italic word is ok, but applying some manual formatting
to the whole document or a whole paragraph isn't usually a good idea.

The docs almost certainly contain lots of manual formatting. Sometimes it's
best to remove all manual paragraph formatting (ResetPara = Ctrl+Q) and font
formatting (Ctrl+Spacebar), and then apply proper paragraph (and possibly
character, list and table) styles.
Or in newer versions of Word, you can use the "styles and formatting" pane.
Turn on "Keep track of formatting" (Tools > Options > Edit), and you see all
the types of manual formatting that have been applied (... visible in the
pane by the missing symbol, ¶ or ª). Use "Select all # instances" again, and
apply a proper style.

Regards,
Klaus