Removing engine block cover

Hi,

Discovered mild leakeage at the top of the engine block of my Suzuki
(GZ125). Adviced by workshop mechanic that the upper engine block gasket has
worn off.

(1) How difficult to replace the gasket if I will to do it myself?

(2) Will it sufficient by just using spanner to lossen and tighten the nuts
on the engine block without any other special tools?

(3) Besides getting a new gasket, any other things require?

(4) Is there any web site that provide guidiance?

(5) What is the life span for a gasket and what causes a gasket to wear off?




Thanks in advance,
YC