First, I commend you on your desire to help infertile couples. Infertility can be a very difficult problem to deal with and egg donation is an excellent way to allow women that are unable to conceive on their own to achieve pregnancy.
Egg harvesting is a minimally invasive procedure that involves the administration of follicle stimulating hormone (FSH) followed by a trans-vaginal need aspiration of the follicles from the ovary. The feasibility of doing the procedure on you depends on where your ovary lies after your hysterectomy. Some of the anatomy in your pelvis changes after the uterus is removed, and the ovary may or may not be safely accessible through the typical approach. The issue with your age will likely be limiting. While there is no technical reason why you could not donate eggs, it is possible that egg donation agencies would decline your offer. This is because eggs from women over the age of 40 are much more likely to result in a baby with Down's syndrome.
I suggest that you schedule an appointment with your OBGYN. You can pose this question to him or her. Most likely, your doctor
will advise you not to pursue egg harvesting. Your doctor may be able to give you advice on how you can help people in some other way. Good luck.