engine gaskets/screws

What is your question?

Hi, I had my car engine swapped 5-6 years ago and it's running fine, except when it's not. just had the oil changed and noticed some leaks. Been keeping an eye on the level for a week and seems to retain adequate oil. Will replacing gaskets help this? The mechanic also pointed out that the sticky black residue on the side of my engine was probably the oil that had seeped out. Thanks. P.S. Anyheads up on a fair and skilled mechanic would be great. I'm new to this area.