Hey guys not really new to the forum been on here for a fair while but dont tend to post much. This may be one of my more noobish posts so it is in the noob section, anyway lets get to the point.

I own a '98 200sx (que for you to boo nissan if you like) and while i think my s14 is great i've started looking for a daily drive/run around car and stumbled upon a 1992 Civic GL. It is a twin carb d15b4 engine with what looks like a 3inch pod filter and steel pipe for intake with a 2 1/4 exhaust system and has clocked almost 250,XXXkms.

Took it for a drive and the car ran surprising well it picked up as best it could, no clutch issues i could feel, brakes were fine and didnt show any signs of stalling even though it sounded like the revs were running a little low. The exhaust is damn loud and drones but i honestly dont care.

The engine has done almost 250,XXX KM so i was just wanting to know:
How long can i expect this engine to last?
Is there a workshop service manual i can download from somewhere?
From people with this engine what type of fuel economy are you getting?
With this many KMs would it be wise to use a 15-40w Mineral oil?
Are Carbs hard to work with? how often would they need cleaning/checking?

performance wise i know this engine is a no go so when the engine decides to blow out and cant be fixed for cost and I was thinking of tossing in a b16 or maybe the d16y1 engine (think that one is the SOHC Vtec unit). When compared to a EG6 is there any major differences in the body? or are the only differences in the brakes, b16 engine etc?

Any help would be very appreciated and advice would be awesome.

Cheers
FenrirWC