It's cake and if you're buddy is replacing just what comes out of the pan, he's doing you a disservice. I drain 5.5 qts out with car on stands in front and ground in the rear then you still have what's in the converter and valvebody. As JCHammond already said there's much more in the system that what is drained.
I followed the below theread, same sprayer, got a infrared temp. Gun from Harbor Freight for $20 and used Valv. Max Life without issue. Simply measure the trans temp. At the pan sump with the gun and at 104*'ish pull the full plug until fluid stops running out then replace. There's a standpipe at the hole so only the "overfill" is running out. If you want to go the extra mile pull the pan and clean the magnets off. Pan gaskets are available from whateverittakes.com. I did mine at 72k for the 1st time and it was nasty, did again 10k miles later and only drained the pan since it was like new. Proves JCHammonds technique gets all the bad fluid out.
Car shifts much smoother after the full flush and fill proving it's not a lifetime fill.
7 Speed Auto Trans Fluid Change