That is how i got started too. I bought the first Colorado (an 08 Ext) for my son in 2018. I spent a few weeks getting it cleaned up and making sure all the maintenance was up to date. During that time I fell in love with it. This year I found myself in need of a winter ride, so I went hunting for one. I got myself a 10 Colorado Reg Cab and have been tinkering with it on weekends to get it ready for the bad weather.
As far as stuff for your boy's truck, it all depends on what he likes. There is still a lot of aftermarket options out there for the 1st gen trucks. Plenty of wheel options, lift/drop kits, LED lamps.
Post some pics and let's see what he is working with.
Man, thats a nice looking truck! Looks like its very well optioned already. He may just have to settle with driving that awesome truck as-is. Great find. Hopefully it will last him through college if he takes good care of it.
Nice truck. Endless possibilities with these trucks. Not to many YouTube builds but there are a lot of builds on Instagram. Good place to figure out what he wants to have done, then just come back on here and ask your questions.