I would've done the same thing, DoK...in fact, I've done it quite a few times, but never with an opossum (yet, anyways). Being on the road for my job, I come across young animals quite often. Being an animal lover, if they need help and after I've come to the conclusion that it's not dangerous to me, I help as quick as I can. I saved (at least for the immediate future) a baby raccoon last year. It was abandoned in the middle of the road and no doubt would've been roadkill if I didn't drive by when I did. I just stayed with it in the middle of the road while calling a local 24 hr emergency vet (already in my phone because this happens quite a bit). The vet thought I was crazy because raccoons are dangerous and might have rabies, but I refused to leave it in the middle of the road. I couldn't get in touch with anyone who would come for it, so I ended up using a newspaper to nudge it out of the road and I ended up picking it up with the paper and leaving it in the nearby woods. It probably died, I don't know...or it's mother may have found him/her, again, I don't know. I see a young raccoon around that area pretty often and I like to think that it's the same raccoon alive because of me.
I have a few cell-phone videos if I can find a way to post them in here, I will...it might've been the cutest thing in the world...but everyone I called told me I couldn't keep it and should never touch it, so I didn't. The vet actually told me to leave it alone altogether, in the middle of the road and all.
In the past few years, I've found kittens, baby birds, turtles (small) and a huge snapping turtle that almost bit my leg off last year lol. The kittens usually come with me and get bottle fed until I find a home for them, same with the birds...but the turtles just shoved to the side of the road lol.
I also found duck eggs when I was in high school. My best-friend and I were in a creek during a storm (pretty smart) and a dam was being washed away with a disheveled nest full of eggs. We didn't know what they were until we took them home and helped hatch 3 out of 5 of them (warm blanket, lamp, etc). One ended up dying, but we found homes for the other 2.
Anyways, good job DoK. A lot of people are f-ed up in the world and would've just had fun running it over...they sicken me.