Well, I would probably blow myself up, so I wouldn't. If you think you can do this without gas leaks, properly, etc ok.
However, you should consider if you need a permit, and if so if DIY is allowed. Or would you skip the permit, which might cause problems down the line.
I would also be concerned that this used model is functioning properly, ie did it get broken when pulling it out? If you have the skill to evaluate that, great, but not everyone does.