Can't really help you much, I've not had either one. Muscle biopsy seems to be ok though, met this elderly man in the hospital who had to do it, and he seemed okay 1-2 days later.
Found this info on nerve biopsy though.
http://healthguide.howstuffworks.com...dictionary.htm
http://www.royalfree.nhs.uk/pip_admi..._biopsy_49.pdf
Hope someone who has done it before will let you know what to expect better!
Btw, why are they asking you to do both?
Do take care and keep us updated!