Is it fine to add in Stop Leak before an oil change for a 2004 Ford Escape?

My father had the Ford Escape and wrecked it, destroying the bumper and pushing part of the hood back. The used-car body shop was able to fix it and put it back on the market. However, I discovered that there were leaks. I haven't really worked on cars before but I'm trying to learn now and I have the things I need for an oil change. When I talked to the clerk about doing the oil change, I also mentioned the leaks, and she advised that I try to stop the leaks first. A friend came along with me and helped me pick out a "Stop Leak", which I know would only be a temporary fix. I had thought about putting it in before I do the oil change this weekend. Is that fine, or should I do it right after the oil change? I know I need to take it to a shop and I plan to, but I need to save up for that. Also, what's a good store to get new carpet? I don't mean the floor mats, either, I mean the actual carpets that goes to the bottom and top of the vehicle. I want to change it to black carpet. I'm working on making it look better for Uber (since I will be driving for them soon.)

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