"While it's open" maintenance- oil pump, rear main, timing?

Okay here's the deal. My 98 4.0 has about 170k on the clock, and I'm looking at doing the rear main seal and oil pan gasket soon. Is there anything else I should replace while I'm in there? I'm thinking I'd probably throw in a new oil pump, but what about stuff like the timing chain and gears? Should I pull all of that too? If I'm going to do that, should I replace the harmonic balancer and water pump too? I don't want to dump too much time and money into this, but if it would be best to take care of it now, I'll do it. Any suggestions?

I would leave the chain and gears if they don't show alot of wear, but I would replace the oil pump and pickup and the harmonic balancer.

i wouldn't even bother w/ the balancer.

If you want to use synthetic oil, you might want to consider changing the front cover crankshaft seal and cover gasket. Other than that, check the timing chain for wear and slack, the connecting rod play, bearing condition and clean the pan out. I did a RMS on my 92 and had no sludge and my new 93 had tons of oil pan sludge. If you have lots of sludge, use a thin oil for 500 miles (5w-20) and change it. One time should do it. Use MMO too.

Why use the 5w-20?

And how do I check the timing chain for wear and slack? Will it be noticable?