Hi there Barna8us, welcome to the forums,
What you are asking is completely doable in CLab. There will be frame-by-frame work (especially animation) and you will probably have to use masks to take out parts of the object at some points, but yes, it is possible. Of course, this really depends on the objects you are using, and the shot itself, but the simple answer is yes.
First, you'll need to take out the original object (except if the object you'll be replacing the first one with is bigger, in which case that would just be an unnecessary headache). Then, put the object you want to add to your video on the timeline, animate it to be the right size, then frame-by-frame, make it follow the running man. You might want to add some blur with the "blur: angle" filter, making it stronger on some frames, weeker on other (you can do that with keyframes!) to match your original footage.
Anyway, once you've finished animating the object frame-by-frame, you'll probably need to mask out some parts of it where the man's arm is in the way (if that's the case). Again, frame-by-frame work will be necessary (CLab doesn't have any tracking abilities, you see).
If you're not familiar with animation, I recommend watching this video tutorial
Also, this text tutorial
might help you with incorporating the different angles of the object together (skip to the part where Tarn talks about animating the flying girl). You're only gonna need that if your camera moves in 3D space, not just following the man in a more-or-less straight line, in which case only 1 picture of the object will do the job.
I hope this answers your question!