Heya Sandman and welcome

Always glad to see new RPers join up and excited about the game.
Regarding introducing your Goa'uld...
You could:
- Do as FairyOracle is doing and do somewhat of a backstory in RP threads. Kinda give the reader an idea of the type of person/alien she is: how merciful, ruthless, cold, vindictive, power-mongering, needy (of worship and adoration and loyalty

), etc.
- You could start with the moment of "occupation"... Maybe your Goa'uld killed his last host and hopped to a new host?
- You could start with a kinda story of his rise to minor power at least and his goal to being a System Lord... Or just ruling a planet... or a people...
... or you could just write and just let him come to life on his own w/o preplanning. I do that alot... have a seed of an idea and then just free-write and see how it grows. Edit, shift, rework.. help the character come alive in my mind and so on...
Or... you could just wait until you are IG and start then.
You might want to contact the System Lords guild (they are RP, from what I understand) if you don't have a guild and ask for pointers there as well.

They have a site- check 'em out on the Command section.