Got a bib for NYC Marathon - New runner advice

24M

So I somehow secured a spot through my company for the NYC marathon this week. I have a history of running so I thought I'd apply on the off chance I got lucky, and did. However I haven't seriously ran in about 4 years. Track/cross country runner all through school, I work out and am decently fit, but haven't trained cardio in awhile.

We have 18 weeks until Nov 1st, so considering I start training seriously starting tonight, eat clean, and dial in, how feasible is it just to finish? I just want to be able to finish and not physically fuck my legs permanently.

This is a bucket list thing for me, I just moved to NYC for work and im only going to be here for another year so I thought this would be a good time to cease the opportunity and do now in my life. Would appreciate any advice.