Few years ago I had Tom Bostic convert my SL8 to a MG36 clone. Since then Ive recently bought a complete G36c kit and I plan on building it into a pistol on a T36 receiver. With my SL8 conversion pretty much everything was done and other than TB working on the receiver it was mostly plug and play. My question is other than installing the barrel, milling the carrier and converting the lower (all things I plan on having TB do) what would actually require "professional" work. In my mind from that point I can just assemble everything together and it should be good to go, or am I overlooking something?

It was an SL8 Rifle first?  And you want to make it into a G36C Pistol?

I would start with not doing that.

ETA: based on your original post, I'm unclear if you're converting the MG36 or building a new kit into a fresh firearm....if the former, you shouldn't do that, if the latter, i retract my comment.

Yes, TB/TB can do all the work required.  Just know that you can't use the same receiver (once a rifle, always a rifle.)

The G36 is actually quite easy to put together yourself; it just requires the mandrel & barrel nut tool from HKParts.