Shireen:
For histological work you would prepare a 10% solution of formalin and put the animal in the solution for 2 - 4 hours to fix the animal , remove, wash and store in 70 % ethyl alcohol.
For genetic work both enzyme and DNA studies put the live animal on dry ice and ship to the researcher.  In a pinch you could crack the shell of the animal and put it in 10 vol. of 95% alcohol  (this would be for small mollusks only)
You can order dissecting tools from any good biological supply house such as Carolina Biological Supply.  Best wishes