Kerb, in the end it's your choice, your decision. Like you I also was majoring in psych.
Long story short, I dropped out 12 hrs short back in the 70's. Did managerial in an office but couldn't stand being inside an office all day. Did career change and was a cop for 10 yrs. Moved cross country and UPS sounded like a good career. Haven't look back since.
Analyze all the benefits from doing this job as compared to other jobs out there. The progression pay scale, pension, health care and make an informed decision that you can live with because in the end it's your choice.
Realize you will most likely begin on the worst (hardest) route until you can bid off it.
Also, find out when your eligible to retire. Under our local it's 25 and out at 57 yoa. That will give some idea how long you have to work before you're eligible for retirement.
Look over to the right under navigation menu - under teamster news, it has the National Contract for 02 -08 and 08 - 13.
Enough rambling, hope this helped tho - jmo.