I see you must have figured out where the slot was, and found that the 4GB card was enough space - at least for now.
But let me tell you that you MAY want to get a larger capacity card for future updates and data storage. I usually recommend at least an 8GB card, which should be large enough for the next couple of years. But these "smaller capacity" cards are becoming harder to find - at least at the local retail level. So as a reference, I have a link to Amazon where is did a search for 8GB microSD cards, where there are lots of good quality cards of that size available.
8GB microSD card SEARCHhttp://amzn.to/1O4tS7k
Also, I wanted to send another link to Garmin's page that mentions the largest capacities and speeds for various units - including the various Nuvi series devices.
By the way, your unit SHOULD be able to handle up to a 32GB microSD (SDHC) and up to Class 10 (speed).
I hope this provides a little bit of more detail about these cards and what your device will most likely need for future updates.
Please let me know if you have any more questions about your device or the update process.
Take Care & Travel Safe, Greg A.
P.S. If you feel this information has been helpful, please feel free to rate MY service level (5-star is my goal) so that I get credit for my time helping you with this question.You should see some "stars" to do that, but please let me know if you do NOT see them (you may have to scroll UP or DOWN) or can not use them.
Also feel free to not rate at all, as I know this information came a bit later than you were looking for.
I see it has been a few days and I just wanted to follow up to see if you have any more questions concerning this issue or if the issue was resolved?
I look forward to any further questions or results that you may have.
Thanks, ***** *****--. .-(im)