Welcome to my life!
the guides ar indeed pressed in, usually driven in an out with driver mounted in an air hammer, although it can be done manually with a hammer. The drawback is someties the hammer methods breaks the guide.(you willneed some sort of piloted driver) After the guides are replaced you WILL need to grind the seats as they will not be concentric with the new guide. Make sure, if you attempt this yourself, that you position the guides the same as the old ones, if too high the retainers will hit the seals, if too low, you might run into the radius under the valve head and not allow it to close fully. In my shop, a complete rebuild on this head would be in the range of 250 -300 bucks, dis-assembly, cleaning, check for cracks, replace guides, grind valves and seats, setting the stem height,checking the springs,setting the installed height of the springs new seals, resurfacing and reassembly. Unless you have the equipment,your in for a lot of work. If you are really lucky, you MIGHT get away just lapping the valves after the guide replacement, but that doesnt happen very often.
If you need any more advice, let me know. Been there 1000's of time in the last 15 years!
Jim