I have a inguinal hernia that needs to be repaired. would it be advisable to have some belly fat removed at the same time?

No: Ill advised to have both done at once - even if you are able to find one willing. You want your hernioplasty to be durable and all attempts at minimizing risk of infection should be followed. More tissue injury = higher risk of infection.

No!: The operations should be kept separate. The complication rate for both is higher if you combine them.