Diesel 603 Head Gasket, Timing Chain & Rails

I have an 87 300TD, with the 6 cylinder turbo diesel engine, the 603.960. It has 168,000 miles on it. I am the second owner. The oringinal owner did frequent oils changes, etc, and there are no records indicating head work or timing chain work. I bought it with 148K. I recently discoverd the right rear corner of the head is beginning to leak oil. I have replaced the valve cover gasket, so I am positive of the location. Is this unusual?

I have the maintenace CD, and plan on replacing the head gasket soon. It looks very simple, with the hardest part probably undoing all the wire connections and plastic clips without cracking everything.

Here is my question, I plan on replacing the timing chain as well. Is there a need to replace the chain rails at the same time? I did a search and did not see much info on the diesels and non-V8's, which are notorious for failing and doing tremendous damage.

Are there any other things I should do while I am in there? I have all new hoses, belts, belt tensioner. Injectors are original, glow plugs unk. I will probably replace all six glow plugs since it will be easy, unless there is sticker shock when I price them.

Thanx in advance for any and all advice.