How can I change specific values in a large text file?

Another approach would be using Perl along with regex. It's really handy for tasks like this. You could run a simple Perl command that modifies the file directly from the command line. Just remember, you'll need to learn a bit about regex if you want to dive deeper, but it’s worth it!

You can solve this easily using `sed`, a powerful command-line tool for text manipulation. Here's a sample command you can run in your terminal:

`sed -E 's/^(([^,]*, ){4}grimoireofgaia:[^,]*, )[^,]*$/15/' input_file.csv`

This command will display the updated output. If you're satisfied with it, you can redirect the changes into a new file like this:
`sed -E 's/^(([^,]*, ){4}grimoireofgaia:[^,]*, )[^,]*$/15/' input_file.csv > output_file.csv`. Give it a shot!

If you're comfortable with Python, you can accomplish this in just a few lines of code. Take a look at this snippet:

```python
with open('filename.csv') as f:
for line in f.readlines():
parts = line.split(',')
if 'grimoireofgaia' in parts[4]:
parts[6] = '5'
print(','.join(parts))
```
As long as you adjust 'filename.csv' to your actual file name, this will work seamlessly!

You can write a quick C++ program to achieve this as well. Just download `g++`, then you can use `stringstream` for reading and processing the lines in your file. Just make sure you pull the values correctly and change them as needed. If Python isn't your thing, this might work out well for you!