I'm a level 96 Vygold Physicist and I'm thinking about paying the 20 GP to change at least my profession, but maybe Race as well. What happens to everything I have done up to this point if I change one or both or my Race & Profession? Would I get some bonus from the Ranks I've already gotten for the Skills my new Race and profession gives me?

You really don't want to switch TO sillix. I'd stay at vygoid until you complete one of the unlockable race chains - and then switch.

vygoid is a very strong race choice for early game if your not in a legion with a large research payout, if you really want to switch do the zolazin mission chain and save the 20GP for a *oooh i want that* moment later. The zolazin chian gives you 3 free race / profession swaps.

rank 313 vygoid excavator

He said Skills, not Sillix. You've got GL on the brain, take a rest lol. Although you are correct, switching to Sillix would be a bad idea due to the dependency it creates.

Vygoid Physicist is not a bad combination, I wouldn't be in a hurry to change away from it.

Not sure what you mean by these last two questions. You won't lose any research you have already done, but your production will lose the 20% bonus. If you move away from physicist your shields will also lose their 30% bonus (divide the current value by 1.3 to see what will be left).

You certainly won't be given any rank points, they will stay allocated just as they were before the change. The bonuses will be as stated in the description for the races and professions, just apply the relevant percentages to the relevant statistics. Were you expecting some kind of special bonus just for changing?

All this is academic, as others and I have pointed out, it would probably be a waste of GP to do this now. Get some Glaviz devices and look at the unlockable races http://galaxylegion.com/wiki/index.php/Races to figure out what you might like to be in future.

Vyg is good choice i would stick with it till you get all basic research done all tho profession a bit useless, especially since at that rank 30% shields isnt that much of a bonus, even more till you havent maxed out your hull shields are pretty crappy, since they are less space efficient..
i am Vyg/excav most of the time since very beginning of the game (been swapping it to Drannik/fixer for wast NPC runs, Inergon/explorer to burn some mission chains and scan planets) by swapping race/pro at right time and for planned stuffs you can gain lots of bonuses

so my suggestion is Vyg/excav till you unlock some more desired race of you own taste

BTW Excavator = +10% to artifact production

so Vyg/excav is ~25% of your production (%age can be different depending on your mining output)