Merging shape files?

Hi:
I like use R for data mining, organization, manipulation and mapping of 
SSURO data of USA. I have already done first two; I need help for 
mapping these data.in R   It will be appreciated if someone helps me to 
solve following three issues:

*1.       How do I merge several  shape files?*
I like to merge several shape files to create a single shape file. All 
files are same structure but different names and in different folders. 
Below I mentioned how all shape files are organized in different folder. 
I want to write a function that I can use to merge the shape files.
 
*File organization:*
?/State_name/soil_ia001/spatial/file_name01.shp
?/State_name/soil_ia003/spatial/file_name03.shp
?/State_name/soil_ia005/spatial/file_name05.shp
.
. ?/State_name/soil_ia21/spatial/file_name21.shp
 
*DBF file associated   all shape files look like below: *
 
ID            AREASYMBOL    SPATIALVER       MUSYM               MUKEY
1              IA001                    2                              
822D2                    402210
2              IA001                     2                              
24C2                      402161
3              IA001                     2                              
93D2                      402217
4              IA001                     2                              
W                           1857266
5              IA001                     2                              
W                           1857266
6              IA001                     2                              
370C                      402177
7              IA001                     2                              
570B                      402190
                -------
 *
2.       My second question is: I like to join a table with this above 
mentioned shape   using a conmen ID like MUKEY.  How do I do this?*
*3.       My third question is: how do I convert this shape file to a 
grid (as a TIFF format or others? ) that I open some other software?*

Thanks
Zia