Are you sure the head gasket is bad at 62k miles?
Are you losing compression?

But...if you do have the head off, I recommend (if you can afford it) doing the valve guides + seals, skim the head and replace coolant hoses (block to water pump).
Once the head is redone, you won't have to worry about it for at least 80k miles.

Also you must consider because the M103 does consume oil over time, the cats + precats eventually get clogged so you'll end up spending anywhere from $300-$1000 to get that fixed depending on your smog state + preference. So if you can prolong the original cat...it will save you money.

For the timing chain...it really depends on how frequent the oil changes were. Check for slack/play in the chain, then look at the plastic guide rails. If they look really worn then replace them as that usually causes premature life on the chain itself due to wearing guides. If you don't see much wear and the chain doesnt make any noises...I wouldn't worry about it. They tend to last anywhere from 100k-300k miles.

If you search my threads I have a complete M103 rebuild with a ton of pics. Might be helpful.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k