How to read a specific section and modify within

Hi, I am n00b to shell scripting and I am learning Ksh, sed and awk. I have a requirement and need your help.

1) How to read a specific section of a file. I have a file and I want to read the contents between say "Page Number:1" to "End of Page 1"
2) Within the section of the file that was read, I need to modify some values say "150" to "1500".

Please help.

sed '/Page Number:1/,/End of Page 1/ s/150/1500/g'  filename

Thanks Kris!!! That worked.