Furnace work?

[crchristopher]

I love this site.    
I am trying to decide whether to buy this '76 clipper (821F?).  When rooting around, I found the furnace very difficult to inspect.  Crammed under the shelving that holds the fridge, and the blower is behind the heat exchange.  What do you do to service the furnace if needed?
Also, any insight into Onan generator?  This one won't crank with a new battery.  Thx!
- Casey