In the UK we can buy CV boots that can be fitted without removing the drive
shaft, I don't know how good they are. The problem with doing the boot only
is iff any grit etc. has got into the joint, try and clean it thoroughly and
replace the grease with one of a similar standard.  If you are just
replacing the boot I do not think there there is any requirement to replace
both boots at the same time, the same is true of the joints if one is OK and
the other not. If one boot has split I would have thought the other boot
will not be far behind and if you can replace them ecomonically it may be
better to do both.

David