I have yellowish dead skin on scalp after my hair transplant. Is this normal?

You should see your surgeon right away. Without any pictures its very difficult to tell what exactly is going on. Severe dead skin across the scalp is not a normal side effect of hair transplantation that we see. Some minor dry skin is normal from time-to-time, but your case sounds more severe. You should meet with an experienced hair restoration surgeon (preferably the one who did your case) or another if you do not trust the doctor. Some shedding of the grafts is normal after hair transplantation, but this usually happens within the first few weeks post-op. Sometimes certain factors can cause adverse effects in hair transplantation. Examples would be mega-sessions or other trauma to the scalp that lead to hair loss and sometimes dead skin. If your surgeons didn't do a mega-session or use robotic tools that can cause trauma, there could be another cause such as an infection. Meeting with a doctor will help you rule out the causes and narrow it down so you know how to treat it. 

It is best to contact your surgeon if you are having issues or questions after surgery since your doctor knows your case best.  The yellow you are seeing may be extra skin or scabbing.  You should not have any of these issues after a month.  Please contact your doctor.

Oozing after a transplant is normal, I suggest you follow proper post op instructions and not pick at the scabs which might dislodge a graft. However, seeing that it as been a month and a half after your procedure, I recommend you refer back to your surgeon to better assess your symptoms.