Steps (DIY/ Do it yourself, this is not a section for lazy people):
1: open gta_sa.exe process
2: get the health address using readprocessmemory and compare the results
3: use writeprocessmemory to change the value of the health address to float/double 32766.0
enjoy.
you can also use cheat engine to get the health address and change values but you want to make your own so.. you know, do it yourself