Before you can spread the pea gravel into the walkway, you'll need a base for it to sit on. Start with a layer of under-layment fabric. This will help keep the walkway flat and stop settling and sagging.

If you till where the pea gravel is going to sit you'll have massive settlement issues.

I am planning on laying down a three-inch tamped solid base of sand underneath the pea gravel. I need to dig down four inches to do so, and I am considering tilling the top three or four inches of topsoil and gravel, which have been compacted by construction.

What I asked is if it is a bad idea to use a tiller on that ground, considering the inch or so of loose gravel that is on top of it.

It wouldn't be my choice to till that but it's not my equipment.

3" of sand is the wrong choice for the base. You want to use 21A/crusher run. You're not going to achieve any decent density of compaction with the sand,

Pea gravel without some type of border to hold it in place becomes an ever spreading maintenance nightmare.

I didn't mention it, but I'm already planning on using edging, brickeyee. what do you think of my question?

I do not really see the point in tilling.

All it is going to do is make more work by loosening up the area, requiring further work to compact it again.

And it takes a lot of small lifts and compaction passes to get back to 'pre-dug' density.

Hand dig it or rent a dingo with a toothed bucket to skim off the soil. I get it, you have access to a tiller so that's what you want to use. That doesn't make it the right tool for the job.