Data sheet is at
http://www.datasheetarchive.com
Search for MB8118160A
As for a replacement... I'd just search for a board with a part # ending in 160 and checking the data sheet for it for compatibility. If it looks good then desolder it and swap it out.
Some of these surface mount RAMs can be very difficult to find replacements for as there aren't a lot of compatible part #s used across multiple manufacturers. It's not like back in the day when folks made a lot of 6164/6264 DRAMs and used similar part #s for most of 'em.
RJ