If it is an easy fix, fix it. If it is a minor leak coming from a major project that isn't cost effective to repair I'd say try to mend it. I'll probably upset some people by recommending an additive aka repair in a bottle, however I have recently had 3 sucessfull ( at least up until the point where I am posting this, hopefully I don't jinx myself) using Blue Devil Oil Stop Leak.
There may be mixed reviews on this product, but like I said I have had some good luck. It's more costly than say some Bars Leak or similar product at about $20 per bottle, but they also offer a money back guarantee. More on this in a second.
One of my father's cars which is an '98 Cirrus with a 2.5l Mitsu V6. The car was my grand mother's. It was a low mileage car but is quite old by today's standards. A little while back at I'm guessing aprox 50k it developed a rear main seal leak. My dad had it repaired at the dealer. He kept getting some spotting on the garage floor afterwards and the dealer told him that it looked like one of the head gaskets was leaking a small amount of oil. It wasn't major and the probably not worth the cost of replacing the head gasket. We put a bottle of the Blue Devil in to see if it helped. With in a week there were no more spots appearing. Power washed the engine both above and below and he has not had this leak come back. That was the first week of June. Still no leak.
My girlfriends Beetle was leaking oil somewhere from the top of the engine. Hard to pin point but it could have been coming from the vacuum pump or something else in that area. It was running down to block and dripping from the bottom of the engine. Enough that after a day or so there was about a 5-6" diameter spot. Thought it was worth a try. Blue Devil in February. No spots since.
Finally, coworkers ram truck was leaking oil. Possible rear main or oil pan. He used it and its been about 5 months and says its seemed to either stop it or at least slow it down to the point where it doesn't seem to noticible.
As far as the guarantee, I wanted to see if they really backed to their product because I was looking into another one of their more expensive products and didn't didnt to risk $50 on a possible fix. I filed a test claim on the VW ( i know this is unethical) repair using the form from their website. One of their tech guys called me a day or so later to help trouble shoot. I explained the original leak, how and when I added to blue devil. Mileage that has been put on since, and that it was still leaking. He apologized and the next week I received a refund check in the mail.
I've tried all sorts of stop leaks over the years trying to save some money on repairs. Most did not work, or only helped for a short period of time. I wouldn't recommend something unless I actually had good results with it, and their product actually seems to work pretty well. I'd say it definitely has a better chance of fixing your problem than a high mileage oil does. This is a specialized product meant to stop a leak. HM oil is a product that is meant to be oil first, with less emphasis on stopping leaks. I think it is worth a try. You really arent risking anything. If it doesn't work you get your money back. If it does, you can be happy and smile because you just fixed an issue with only $20.
Just my thoughts