Finishing last isn't something to be afraid of it means you are still ahead of the 99% at home on their sofas.
I did my first "race" on Sunday 506 out of 525 finishers. Before it I was at times silly enough to worry would it be respectable what if I am last, etc.... It's totally irrelevant it's not a race against other people unless you are in the top 10. It's about you and the new friends you meet on course, all beating the course in any way possible by finishing ;/)
When you have finished a fee then I think you can start to plan where you would like to be, but take it from me I'm damn competitive, never let anyone else win at monopoly, it's not like that. If you complete it, you will feel 50ft tall.
Steph