Actually, there are photos of one person's mapping job of Level 1, and he claims that the maps are more like 200x200. Pete's page is a tribute to Telengard at the following site which has several links to other resources (as well as a win32 port of the game) and the photos:

Imagine the following dimensions, 200x200x50. This is a non-random dungeon of monumental size. Pretty amazing for a game that was written entirely in BASIC in 1983, no?

More specifically, the particular line to hack to give you copious amounts of experience (using the C=64 emulated version) is:

3223 E=ML*M*10:EX=EX+E:GOSUB19000

just change the 10 to whatever multiplier you want.