I recently changed from a stick to a spectrum DXC3 wheel transmitter and wondered if anyone has any advice

Practice! Practice! Practice! You will need to retrain yourself and your muscle memory so it becomes natural to use the different style radio. If you race an onroad car that doesn't work well off the track, buy some basher/buggy vehicle to run out in the street or parking lot to get used driving that way.

Also check out the VRC program to get cheap practice time in as well.