My condolences on the loss of your grandma.
Go to church, sit with the family and friends, and do what everybody else does, except don’t go to Communion unless you’ve confessed beforehand and are planning on being a regular Mass goer and avoiding all sins going forward.
A Mass is a Mass is a Mass. The only difference for a funeral is the Mass uses special prayers and readings relating to a funeral, and also the body is usually present. The priest may or may not permit relatives to read a eulogy during announcement time, if relatives even want to do that. I know when my parents died the last thing I wanted to do was get up and make a speech, but my cousin did it when their parent passed. Generally this is arranged in advance if it’s going to happen at all.
In any event, if this is your grandma, no one is going to be looking to see if you make a mistake. If you do make one, like stand when others sit, people will excuse it because you’re grieving.