Is the splenectomy a risky thing to do?

No. There are open and laparoscopic options for some people who need splenectomy. There are a variety of reasons of blood disorder, some cancers, and sometime traumatic injury that may need splenectomy surgery. Your surgeon would discuss and review specific surgical risks for your own specific situation.
Early&Late Risks. Splenectomy is usually performed as an emergency operation after trauma or an elective operation to treat hematologic diseases. Early risks include bleeding requiring transfusion and injury to adjacent organs including the stomach and colon. Late risks are related to an increased risk of infection from encapsulated bacteria, necessitating periodic immunizations for extra protection.
Maybe. Splenectomy is done for many reasons - the reasons themselves make up most of the risk. For itp ( low platelet count probably immunologic) - splenectomy can be done with a laparoscope and has relatively low risk. If splenectomy is done for massive enlargement due to certain hematologic reasons - the risk can be significant. Make sure your surgeon is experienced in splenectomy.