Gary is right, they are different. Depending on a person's accent (and how the word is being used grammatically), "to" can sounds like /d/ in some cases, or it can sound like /t/, or like "too" (the same pronunciation as the number "two"). The word "the" should always be pronounced with a voiced /th/ sound (except in a few specific, non-standard accents of English). To make the /th/ sound, your tongue should touch the back of your upper teeth -- not the roof of the mouth, which makes the sound /d/.

Thank you!

No. I'll leave this to a teacher to explain properly, but they are definitely different. The 'th' sound is one of the most commonly mispronounced sounds in English. If you are making the th sound correctly, and do it continually, you should end up with a numb tongue!