UNIX for Dummies Questions & Answers

I am trying to do the following using awk (is that the best way?):

Read 2 files created from the output of df (say, on different days) and compare the entries using the 1st (FileSys) and 6th (Mount) fields to see if the size has changed. Output (at least), to a new file (some header lines) and each record's fields $1, $6, the 2 dir sizes and the delta. Plus append any unmatched lines from the file1.

I have an example (from here) that I'm trying to decipher and adapt to my purpose but am having a difficult time figuring it all out.

Code:

awk 'NR==FNR {A[$1]=$2; next}A[$1]{$1=A[$1]}1' FS=\| OFS=, file1 file2

Any help would (duh!) be greatly appreciated.

Thanx
Renata

Post sample input and desired output files.

Roughly this is the format of the files (output from the 'df'
would be a straight dump into Filex.

Maybe awk isn't the right tool?
Thanx
Renata

File1 2/25/2011
Filesystem Size Used Available Capacity Mounted on
/prod 390MB 7398944 29834728 18% /data
/prod/ 252.1MB 1234557 32012367 51% /apps/DPEAS
/prod/ 565.4 MB 217138.6 30256894 10% /data/DPEAS
EOF

File2 2/24/2011
Filesystem Size Used Available Capacity Mounted on
/prod 350MB 7398904 29834768 20% /data
/prod/ 262.1MB 1234567 32012357 50% /apps/DPEAS
/prod/ 565.4MB 217138.6 30256894 10% /data/DPEAS
/home/ 742MB 123456 12345678 16% /MIRS
EOF

Output File
Prev Date 2/24/2011
Curr Date 2/25/2011

old size new size delta filename
350MB 390MB 40 MB /prod/data
262.1MB 252.1MB -10 MB /prod/apps/DPEAS
565.4MB 565.4MB 0 MB /prod/data/DPEAS

742MB /home/MIRS
EOF