Looking for some info on the old Omega

Looks like 166.020 from mid 60's, this is a front loader requires special technique and tools to open from front not for beginners. Also looks like bad damage on dial at 6:00 marker. Hard pass move on
Its good idea to indicate some info on watch and whether you own it or are considering purchase, etc

read this for guidance

I have heard that some watchmakers are able to remove those crystals with a generic Bergeon 4266 lift, but to me that doesn't look as safe or reliable as the official Omega tool. In either case I don't think it's a simple operation.

Once you are certain about the case reference, you can identify the correct crystal using reference information like in this thread:

With the crystal number known, you can often track them down on eBay. Buying appropriate tools will be a significant expense, but possibly worth it if you expect to be working on watches often.

You don’t need any special tools to remove and replace the bezel and crystal but you do need the right technique, otherwise you risk damaging the bezel and/or crystal. Once you know what you’re doing a case knife is pretty much the only tool you need.

However, these crystals are hard to find on the open market as Omega no longer sells parts to third party suppliers. Your options are really;
1, send the watch to a watchmaker with an Omega parts account (but they will likely only replace the crystal as part of a full service).
2. Keep an eye out on eBay, but be prepared for a long wait and it won’t be cheap when it comes up (then you run the risk of damaging it by installing yourself if you’re not sure how to do it).
3. Use a generic crystal (not always a great idea on DeVilles as the crystal is so specific, but some generics do work).
4. Try and polish the crystal you have.

I would always exhaust option 4 before trying any of the others.