HELP PLEASE!! OLD GANESH PLAQUE/RELIGOUS ITEM

Hi all,
I would really appreciate some help with this item.
I bought this from a second hand shop only a couple of hours ago.
It is a small wooden plaque, which features Ganesh seated on the back of a RAT.
It measures approx 5inches wide and 4inches high.
It has a couple of small holes at the top in the middle which look like they would of been used for a cord rather than used to hang from a nail.
It is extremely dirty, but there seems to be much better detail underneath the dirt.

I would like to know the best way of cleaning out the dirt without damaging the item as it already has a few cracks.

Also an age......It appears quite ancient and is cruedly carved.
Thanks Ian