How will Drill Sergeants treat prior service coming into training ?

That is going to depend on the Drill Sergeants you get/have. I've reclassed twice (to 12B and 68S), and both times the Drill Sergeants left us Prior Service alone. They may put you in charge.....they may not. They may send you down the hall away from the IETs or not. Sadly, you will just have to wait and see when you get there and report in.

Depends on how you perform.
Perform like a Soldier, and you'll be treated just fine.
Be proactive, and help other Soldiers.
Keep in mind that it's not just the DSs, but the entry level Soldiers will have spent a couple of months together, and they will also have some expectations, cliques, etc.
Hopefully, you have been doing some hard physical training, so are at the same level of fitness as they are. If not, both the DSs and other Soldiers are going to take issue with it, even if they say nothing.
You'll do fine, and you'll be treated better, as long as you perform.
Best wishes.

We had a couple reclass guys who jumped into Week 7 or 8 of my OSUT. They were treated with a greater measure of respect than the rest of us, and as they were always on their game, they never gave reason for the DS to come down on them, like...ever. The rest of us looked to them for guidance and they were able to help us out a lot. These reclass guys had never left the service, so they weren't the purest form of "prior service" as they never had a period of separation, so I don't know if that difference matters or not.

Good luck!