No don't panic
in a nutshell...
Test: Test Exemption is probably on the V112G form (downloadable from the net) although theres a bit of a review on at the moment regarding exemption elligability (check out Antar Mikes thread on the subject he's our man in Havannah)
Tax: yes you must show a current one as you would with the car but you simply don't get charged for it at the post office...12 months free :-D
Same rigmeroll at the post office... log book, current insurance and MOT (or in the case of the GMC probably the V112g form... I think, in place of an MOT certificate)