The vedas themselves endorse the puranas.
rcah samani chandamsi puranam yajusa saha
ucchistaj-jajnire sarve divi deva divi-sritah
"The Rg, Sama, Yajur and Atharva became manifest from the Lord, along with the Puranas and all the Devas residing in the heavens." (Atharva Veda 11.7.24)
sa brhatim disam anu vyacalat tam itihasas ca puranam ca gathas ca itihasasya ca sa vai puranasya ca gathanam ca narasamsinam ca priyam dhama bhavati ya evam veda
"He approached the brhati meter, and thus the Itihasas, Puranas, Gathas and Narasamsis became favorable to him. One who knows this verily becomes the beloved abode of the Itihasas, Puranas, Gathas and Narasamsis." (Atharva Veda 15.6.1012)
evam ime sarva veda nirmitah sa-kalpah sa-rahasyah sa-brahmanah sopanisatkah setihasah sanvakhyatah sa-puranan
"In this way, all the Vedas were manifested along with the Kalpas, Rahasyas, Brahmanas, Upanisads, Itihasas, Anvakhyatas and the Puranas." (Gopatha Brahmana, purva 2.10)
nama va rg-vedo yajur-vedah sama-veda atharvanas caturtha itihasa-puranah pancamo vedanam vedah
"Indeed, Rg, Yajur, Sama and Atharva are the names of the four Vedas. The Itihasas and Puranas are the fifth Veda." (Kauthumiya Chandogya Upanisad 7.1.4)
asya mahato bhutasya nihsvasitam etad yad rg-vedo yajur-vedah sama
vedotharvangirasa itihasah puranam ityadina
"O Maitreya, the Rg, Yajur, Sama and Atharva Vedas as well as the Itihasas and the Puranas all manifest from the breathing of the Lord." (Madhyandina-sruti, Brhad-aranyaka Upanisad 2.4.10)
Taittiriya Aranyaka (2.9) states yad brahmananitihasa-puranani: "The Itihasas and Puranas are Vedas."
For reincarnation in the vedas see-
Reincarnation and Karma in the Veda Samahita - Hindu Dharma Forums
For proof that Shiva and vishnu are not minor gods in the vedas-
Lord Shiva in The Vedas - Hindu Dharma Forums
nArAyaNa in the veda-s - Hindu Dharma Forums