D-Link DIR-853 A1 vs A3 vs R1 can I install open wrt?

Hi all.
Just purchased a D-Link DIR-853 on the basis that it had the right features for me and looked like it would be compatible with OpenWRT when I searched the TOH.
I just recieved the box and it has HW ver A1, and the TOH shows compatability for A3 and R1.
Now i'm not sure enough about all of this to know if it's worth attempting given its not an exact match.
I did some reading on here an google, and can't find anything definitive on compatability, or what the differences are between these HW revisions.
Its annoying that the versions are not specified when buying online.
can anyone out here who knows more than I, please enlighten me as to what my options are here?
Is there a compatible build in existance?
is customising a new build something that I could accomplish, being about 1 or 2 steps above absolute beginner at linux?
thanks in advance.