Tramadol is not a benzo, it's a (somewhat atypical) opioid. I'm not sure how long they keep for - there's no expiration date anywhere?
They work... somewhat similarly to oxycodone, but are nowhere nearly as strong. Oxycodone is one of the more stimulating opioids, but it is a very potent one, compared to tramadol which ranks between codeine and hydrocodone. It's also got mild SNRI properties. Have you got a tolerance? If not, I would suggest starting with 100-150mg, and taking more at 50mg increments (every 30-60 minutes or so) until you feel good - without a tolerance, 200-300mg should have you feeling pretty nice. Tramadol also has increased bioavailability with repeated dosing, so it's better to take it a little at a time than all at once). Don't exceed 400mg - it could make you feel quite sick, and at doses above that it's also known to induce spasms and seizures - very dangerous.
The feeling is nowhere as heavy or intense as oxycodone, but lasts for longer - feels something like a mix between an opioid and low-dose MDMA for me. I think 100mg of tramadol is about equipotent to 5mg of oxycodone.
If you aren't on any SSRI/SNRI medication, they should be pretty safe to use (except I don't know how long they stay good for - I'm assuming 2 years old tablets shuld still be safe), but watch out with combining them and anything serotonergic - that's asking for trouble.