[JFP in PA]

On a five-chain engine, you are locking the exhaust cam on one cylinder head. In reality, you could lock either side, but the passenger side head, with the green cam cover plug towards the front of the car is way easier to get at and see if the cam slot is in the correct position, so it is the one preferred by those of us that do this on a regular basis and need to work quickly and cleanly.

The third hydraulic tensioner is underneath the AC unit on the top of the engine.

If you removed the IMS flange cover with the engine locked at TDC and no cam lock in place, you have a better than even chance that at least one chain has jumped time, usually indicated by the IMS shaft pulling to one side. With the shaft in this position, you cannot pull the bearing out, and the cams will need to be reallocated to get everything back to where it should be. That would require access to some special tooling and knowledge of how the cams are allocated. This process is not hard but is complicated and cannot be done without the correct tool.

The only place that spring could have come from is either front or ream main oil seals. In any case, you should be replacing the RMS with the new PTFE upgraded seal whenever doing any IMS work as it is a $20 part and accessible when the trans is out but again requires a special tool to install it correctly. LN rents this tool for DIY installs. They may also have the cam allocation tool as well, but you will need to check with them on that if you need to do the cams.