Find a reputable engine builder in your area.
Local to me- $1,680 for a rebuilt 2.5, +tax and core.
If you are going to have yours rebuilt, it will be a two week process. You pull, break down, clean parts, take block and head to machine shop, research and shop for new parts, order.....wait on shop.......get parts.....begin rebuild.....etc......
So, you'll need time and a garage and tools.....hoist and engine stand....etc.. and KNOWLEDGE!
Bottom line cost? on the cheap side- $2300. There will always be the unforeseen- new mounts? new starter? new cables? new clutch?........etc...........
You'll get a good 100-150K miles out of it.