engine work

[dtrain]

89 420 sel 196k

Recently replaced the timing chain, guides, etc. - thanks to the forum.

There is a ticking noise in the engine (different from the chain slap from before) that I believe is one or more lifters. It ticks all the time (warm and cold engine) and has not changed with several oil changes (based on suggestions through the forum). In addition, there is oil on the #6, 7 and 8 plugs. My questions:

Can i just replace the seals to take care of the oil on the plugs? It doesn't burn oil and runs really well. Should I replace them all (intake and exhaust)?

I have read details about how to determine which lifter(s) are bad but what parts should I replace once I find the culprit(s)?

Should I plan on picking up any special tools for either job?

Thanks in advance for any suggestions.