honestly.....the engine side of thing was the fastest part of my project id say. I had it bought,built,painted and ready to dunk in after jsut a few days time. The sanding,primer,painting ,wiring etc...etc... of the engine bay however was a different story. but once I had it painted and ready for the engine...it literally took me and my father 15 minutes to get the engine on the cherry picker and down into the engine bay and mounted on the engine mounts.not sure what you need to do to the engine bay?....tidy up wiring?....or overhaul the paint.
either way ...I would say get to work on it now!....you could have the old engine out in a night easily.....and if you do need to paint and tidy up some wiring.....you might be looking at a weeks worth of work maybe a little less or a little more depending on if you have an extra set of hands....to get it prepped and painted. and the wiring is nothing...that would go fast.
I would say that if you had another guy helping you and jambed on it...you could pull the engine,restore the bay,install the new engine in about 2 weeks.
I know i kow...easier said than done lol...cold weather,space to work,family time,finding someone with time to help,cash....and so on....just trying to let you know it can be done.
as for material cost .....I would think that around $100.00 would cover (even less if you still have left over paint from doing the exterior!).
but...if you could get it done now...you would be ready to rock come spring time!. or you could do the same stuff come spring....BUT you will have to live with the agony of not being able to drive it while its out of commission lol.
boils down to how bad you want to get it in there,your funds and your free time to get it done.
if none of it meshes wells,then you may just want to put it on the back burner as a project for next winter.