The degree of blowby is not significantly affected by valve seal or valve guide wear.
There is always SOME blowby in an engine caused by a less than perfect ring seal. If it is not enough to cause blue smoke at the tailpipe why not consider installing a PCV valve vented into your intake. That would be a lot cheaper than valve guide or head work.
Before you decide to tear into the engine do a cylinder LEAKDOWN test. Also Moroso makes an inexpensive ($80) blowby meter. Those two tests will tell you a lot. Good luck.
