Low compression = valve replacement '93 metro

I just bought my metro, I was told it has a sleepy valve and won't pass emissions.
If I'm going to do a valve replacement, What am I in for?
(i.e.) Can I do it in a day, or do I need to plan for a week?

I would probably just get a rebuilt head and swap it. Change the timing belt while it is apart. You could do it in a day without trying to repair the old head.

ok thanks!