Rabbi Hershel Reichman
The main issue for Ashkenazim eating in a Sephardi home on Pesach is 'kitniyos', which includes rice, corn, and certain legumes.
According to the Rema, the custom of Ashkenazim is not to eat kitniyot on Pesach. Sephardim do eat kitniyot. You will have to ask your personal Rabbi to ascertain which foods appy to you, as the list varies according to community and custom.The prohibition of kitniyot according to the Rema only applies to foods in which the majority ingredient is kitniyot, so for example an Ashkenazi should not eat plain rice, but would be allowed to eat meat cooked together with rice, if he would eat the meat seperately, even if it has some 'taam', flavor, of the rice.
To avoid problems, it is probably advisable not to eat any food whch has rice or othr kitniyos ingredients. There is no problem for an Askenazi to use the plates or pots that were used to cook or serve kitniyot by Sephardim on Pesach.
In short, you can attend a Sephardi seder and use the plates, silverware and other dishes. Just make sure that the food you eat is not kitniyos.
Rabbi H. Reichman