I think Guru Granth contains words from 26 different languages. Its best if you can read punjabi, that doesn't mean you will fully understand Guru Granth saheb- for that Gurmukhi to present day punjabi translation is required. All this is available in SIKHNET - Sikh Religion - Sikhism Information.
Guru Granth is unique its written in poetic form, just like a song, a poem from one language can't be translated to another only the meaning or what they are on about can be captued, the same rule applies. So if you really wanna admire what is written then learn punjabi. its worth it. if you can't then plenty of translation are available on that site and translation of daily hukumnamas etc.