Is the 98 in military configuration? If so, you will want to change the safety to a low swing 3 position to clear a scope, probably. Anywhere from 70 to several hundred dollars for that. You will probably want to have it drilled and tapped for a scope mount, plus the bases, scope mounts and scope. The military 2 stage trigger should be replaced for a decent trigger pull. About 70 for a Timney, plus installation.
I would leave the trap door magazine. It is certainly quicker to unload, and safer than running the shells through the action. A new barrel would probably be several hundred dollars plus fitting, then bluing the whole thing. You better check with a smith to find out if the longer 30-06 fits in the mauser action, and if it does, will it with heavier longer bullet weights? What do you have for a stock?
By the time you are done, plan on having the cost of a new gun invested, just for what is discussed. I also have a 98 that I have planned to do this, working through a well known local gunsmith. It was cheaper and much more practical to buy a new Ruger 77 Mk11 in .308, which is an excellent Mauser clone. You could pick at it and do it on the cheap, but it will shoot and look like it too. Inquire with local gunsmiths where you are, and look at their work. Some, like mine, will do it a bit at a time as you can afford it.