There are indeed merits for writing sutras.... especially so in
the past, where there is no photocopying machine, and everything
has to be hand written. If you can copy the sutra, and pass it to
someone else, isn't that great merits? But even today... there are
still merits. Because by copying the sutra you will also deeply
look into the content of the sutra, and that itself is great
merits. And I believe somehow if you copy the sutra by hand, you
will treasure it more because it is done with great effort. And
even to keep, recite, read, and expound the sutras, all these have
very vast merits that are immeasurable 
As for Mantra wheels, I am not a Tibetan Buddhist but you can refer
to this article which is well written on this subject: http://www.fpmt.org/resources/lzrbenefits.asp