2002 Buick Rendezvous Water in the engine

I have a 2002 Rendezvous CXL.

Just bought it. The Previous owners had problems with overheating so they took it to a shop. They were told that it needed a new engine.

I talked to him and it sounded like it may have needed just a new head gasket, and possibly a remanufacture job on the head itself.

We brought it home and did a compression test on it.

Cylinder results:

#1=148
#3=150
#5=150

#2=153
#4=150
#6=150

It starts, and will run, but I noticed that the gap on the plugs was close to 80 on a couple.

Possibly the original plugs?

The main issue that was found was foam on the oil cap, leading me to believe that there is water in and/or getting into the engine somehow.

Previous owners said they filled the overflow before they drove it, but it still resulted in overheating.

It sat for about 6 months before I picked it up to work on yesterday.

The overflow is dry, and the radiator is 1"-1.5" low.

Any thoughts?

Thanks