Just like @LoyceV said, remove the HDD before giving the device to someone else. If they ask why the HDD is missing, you could say you need the data for urgent work and ask them to use their own HDD/USB drive for testing.
I am not sure many laptop allows for an easy HDD removal, even more without breaking warrant (Mac User anyone?).
Also,even if I haven’t any wallet in it, just having access to my email a malicious user could do extremely dangerous actions.
Basically, when to give your laptop to an external technician, you are trusting him not to rip you off.
Maybe it’s worth asking him to assist in person to your repair, so that you don’t leave him with your datas alone. This could be counterproductive for opsec reasons anyway.