You'll probably get a fine for abandoning, and then your haulage will now be stolen cargo. Either find a station that has a black market (in Contacts at the station if it has one) and then abandon your mission there (and sell your now-stolen loot), or alternatively dump it in space away from a station so you don't get a "littering" fine too. Note you can't dump or sell your Haulage till you abandon the mission.
After that, just check out what kinds of routes you can ply with your current ship at max cap, with the Galaxy map. It'll give you an idea of what kinds of ranges you're working with, and then just make sure you can get back to where your mission is. I pulled a lot of fast-one-way, long-back-way missions before I could work myself into a larger ship with better range, but there are plenty of binary-system trade runs that can be found even inside a relatively small jump range.
