Most people don't have any issues with their guns, even older ones. There's nothing to be nervous about. FTEs and FTFs are a fact of life with all guns so don't worry about those. If you're concerned about OOB issues, don't do rapid fire and make sure the bolt is all the way forward between shots. If you don't have any problems for your first session then you probably don't have to worry. If you have a lot of FTEs or FTFs (e.g. more than one per magazine) then you should send it in and they will update everything for you.