As hopey said - physio is a must for CRPS/RSD! It is painful - I've had it for 13 years, been full body for nearly four, - but without even gentle therapy we risk severe muscle atrophy, joint changes, osteoporosis. CRPS has also been shown to cause something like a 'neglect syndrome'. I have this problem particularly with my legs, which are worst affected (my right knee was my original site) - where my legs feel completely separate from my body - as though they aren't really mine. I 'tell' them to do something and even though they feel like they're moving, like the muscles are contracting, nothing is actually happening. Physio and 'brain training' can help a lot with this.
Different physios will use a different techniques, but my personal guideline for anything is that a little extra pain is okay. Anything causing a lot of extra pain, or pain lasting more than an hour or two after is not. Do you know if the physio is knowledgeable about
CRPS? If he/she doesn't bring it up themselves, ask them about
Graded Motor Imagery - and have a look yourself at Graded Motor Imagery
and also search for 'Recognise' - if you wish to, you're able to register so that you can do a trial of their laterality program. This can help with the limb recognition problem I mentioned above.
Best of luck - and please keep us informed.