Seems there is [oil in the coolant] but [no coolant in the oil]. There is a small oil leak on the right (spark plug) side of engine along the gasket.

Q's...
1. Is it a bad head gasket?
2. If so, how easy is it to replace the gasket? I have lots of tools and will power.
3. Seems to run ok at highway speed but stumbles and hesitates on heavy acceleration?

Distinguish engine from transmission oil in the coolant. The former almost invariably means head gasket; the latter a failing radiator transmission cooler. Both are big problems. If you are running the original radiator, you need a new one in any event. See the FAQ for tips.
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See the 700/900 FAQ at the select shortcut button on the top right of the screen.

Installed new radiator a few weeks ago thinking it might solve my problem - needed one anyway. Radiator and engine oil are both clean.

Seems everything points to failed head gasket then, right? Maybe I should try some of that "miracle" head gasket fixer you find in auto stores and pour into the radiator. What do you think?

How long can I ignore this problem before its critical?

Whatever you do, do not put an additive in the radiator to try and fix the leak! What that is doing is damming the gasket tear with sealer, and anything else that should be marginally flowing water.

If your oil is in the water and not vice versa, do everything that you can to reduce crankcase pressure and buy a little time. You already have a head gasket problem that is not going to get better so start planning on changing it, which is not a very difficult job, especially if you use the FAQs.

BTW, Just my opinion based on 50 years of experience, not counting my first 10 years, :)

Regards

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Will Dallas, www.willdallas.us, www.willdallas.org, www.willdallas.com, www.dallasprecision.com 86 245 DL 222K miles, 93 940 260K miles, 88 765 GLE 152K miles

Any ideas on how to reduce crank case pressure for now?

Make certain that your flame trap is clean and the oil separator is functioning. Clean it if necessary. Make certain to read the FAQs about checking for crankcase pressure buildup.

Regards,
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Will Dallas, www.willdallas.us, www.willdallas.org, www.willdallas.com, www.dallasprecision.com 86 245 DL 222K miles, 93 940 260K miles, 88 765 GLE 152K miles