That depends. If you want to set German as the interface language, you will have to get a German version, but if you just want to have it produce German characters and spell check German, no. All you would have to do for the spell checking is buy the German language pack from Microsoft.
First, the steps to switch the spell checker.
1. The proofing tools for the appropriate language have to be installed.
2. Press CTRL/A to select the entire document.
3. Click the Review tab on the Ribbon.
4. In the Proofing section, click Set Language.
5. Select the language you want in the list box.
6. If you want to make this the default language for future documents, click the Default button.
7. Click Yes in the message box.
8. Click OK.
Now to get German characters:
1. Make sure your keyboard is in NumLock mode.
2. Hold down the ALT key and enter the number on the numeric keypad. (Note that many laptops have a blue FN key that changes a set of keys, also with blue numbers on them and usually in the 7-8-9-U-I-O area, into a numeric keypad.)
for Ç use 128
for ü use 129
for é use 130
for â use 131
for ä use 132
for à use 133
for å use 134
for ç use 135
for ê use 136
for ë use 137
for è use 138
for ï use 139
for î use 140
for ì use 141
for Ä use 142
for Å use 143
for É use 144
for æ use 145
for Æ use 146
for ô use 147
for ö use 148
for ò use 149
for û use 150
for ù use 151
for ÿ use 152
for Ö use 153
for Ü use 154
for á use 160
for í use 161
for ó use 162
for ú use 163
Hope that helps.